Financial Guides & Resources
Plain-English guides covering savings, investing, loans, mortgages, and affordability.
Our guides are written to be paired with the free calculators on CalcGrowth — so every concept is something you can immediately model with your own numbers. Each guide is reviewed for accuracy, kept up to date, and intentionally free of sales pitches, affiliate pressure, or vague advice. We focus on the math, the trade-offs, and the realistic ranges most people actually need.
The library is organized into three core areas: savings & investing (how compounding really works, what to expect from monthly contributions, how to set retirement targets), mortgage & affordability (what you can really afford, deposit math, rules of thumb, monthly payment breakdowns at common loan sizes), and loans & debt (snowball vs avalanche, refinancing math, paying off cards and car loans faster). Use the categories below to jump in, or open a hub for a curated learning path.
How to use this library: if you're early in a decision, start with the relevant hub and read the pillar guide first — it gives you the framework. If you have a specific question (“what does $300/month for 30 years grow to?”, “can I afford a $400K house on $90K?”), search or scan the titles below. Every guide links out to the matching calculator so you can plug in your own numbers in seconds.
Why we publish these guides
Most personal-finance content online is either gated behind a product pitch or written so generically that it doesn't help anyone make a decision. We try to do the opposite: explain the underlying math, show a few realistic scenarios with numbers, flag the common mistakes, and link to the calculator that lets you run your own version. None of this is financial advice — it's education designed to make you a smarter user of the calculators on this site and a more confident decision-maker with your own money.
No jargon walls. Every formula is explained with a worked example.
Every guide links to the tool that lets you model your own scenario.
No affiliate steering, no lender referrals, no upsells.
Savings & Investing
Build long-term wealth with compounding, monthly savings strategies, and realistic return assumptions.
How Compound Interest Works
The mechanics of compounding explained in plain English — with charts and examples.
Read guideThe Compound Interest Formula
A=P(1+r/n)^(nt) — broken down step by step with realistic worked examples.
Read guideSimple vs Compound Interest
When each applies, how the math differs, and why compounding wins long-term.
Read guideHow to Save Money Faster
Practical, repeatable tactics for boosting your monthly savings rate.
Read guideHow Long Does It Take to Save $10,000?
Timelines for hitting $10K at different monthly contribution amounts.
Read guideHow to Save $10,000 Fast
An aggressive 6–12 month playbook for hitting $10K quickly.
Read guideHow Much Should I Save Each Month?
Benchmarks by income and goal — plus a quick formula you can apply tonight.
Read guideHow to Plan a Savings Goal
Turn any savings target into a realistic monthly plan in 5 steps.
Read guideHow Much Will $100 a Month Grow To?
$100/month invested at a 7% average return grows to about $17,400 in 10 years, $52,000 in 20 years, and $122,000 in 30 years. The longer…
Read guideHow Much Will $500 a Month Grow To?
$500/month at 7% becomes roughly $87,000 in 10 years, $262,000 in 20 years, and $612,000 in 30 years. At 10% (long-term stock market aver…
Read guideHow Long Does It Take to Reach $1 Million?
At a 7% return, saving $500/month reaches $1M in about 36 years. $1,000/month gets there in about 28 years. $2,000/month does it in about…
Read guideEmergency Fund: How Much Should You Save?
Most people need 3–6 months of essential expenses in cash. Single-income households or freelancers should aim for 6–9 months. The starter…
Read guideSavings by Age: Are You On Track?
A common rule of thumb (Fidelity): 1× salary saved by 30, 3× by 40, 6× by 50, 8× by 60, 10× by 67. So if you earn $80K, target $80K by 30…
Read guideCompound Interest: Monthly vs Yearly
On a $10,000 balance at 5% for 10 years, yearly compounding gives $16,289. Monthly compounding gives $16,470. Daily compounding gives $16…
Read guideWhy Starting Early Matters More Than Amount
Someone who saves $200/month from 22 to 32 (then stops) usually ends up with more by retirement than someone who saves $200/month from 32…
Read guideHow Inflation Affects Your Savings
$10,000 in cash today is worth about $7,400 in 10 years at 3% inflation. To preserve purchasing power, your money has to earn at least th…
Read guideBest Interest Rate Assumptions to Use
Standard defaults: 4–5% for high-yield savings, 4–6% for bonds, 7% for diversified stocks (real, after inflation) or 9–10% (nominal). Use…
Read guideBeginner's Guide to Investing Consistently
Open a brokerage account or 401(k), invest in a low-cost broad index fund (like an S&P 500 or total-market fund), automate monthly contri…
Read guideHow Much Will $1,000 a Month Grow To?
$1,000/month invested at 7% grows to about $174,000 in 10 years, $524,000 in 20 years, and $1.22 million in 30 years. The longer the hori…
Read guideHow Much Should I Save by Age 30?
A common benchmark is to have 1× your annual salary saved by age 30 (e.g. $50K saved on a $50K income). If you're behind, focus on gettin…
Read guideHow Much Should I Save by Age 40?
By age 40, a common benchmark is to have 3× your annual salary saved (e.g. $240K on an $80K income). The realistic median is much lower —…
Read guideHow Much Money Do You Need to Retire?
A common rule of thumb is 25× your annual expenses. If you spend $50,000/year in retirement, aim for $1.25 million. If you spend $80,000/…
Read guide7 Best Compound Interest Examples (with Real Numbers)
The most powerful compound interest example: investing $200/month from age 25 to 65 at 8% grows to about $700,000 — yet only $96,000 of t…
Read guideHow Long Does It Take to Double Your Money?
Divide 72 by your annual return rate. At 6% your money doubles in 12 years; at 8% it's 9 years; at 10% it's roughly 7 years. This shortcu…
Read guideBest Savings Rate by Income (How Much to Save)
A widely cited benchmark is to save 20% of gross income (50/30/20 rule). Lower incomes should aim for 5–10% to start; higher incomes shou…
Read guideHow Much Will $2,000 a Month Grow To?
$2,000/month invested at a 7% average return grows to about $347,000 in 10 years, $1.05 million in 20 years, and $2.44 million in 30 year…
Read guideBest Compound Interest Strategy for Beginners
The best beginner compound interest strategy is: start now (not later), automate monthly contributions, invest in a broad low-cost index…
Read guideCan You Retire With $1 Million?
Yes, $1 million is usually enough to retire on if you stop working at 65 and spend around $40,000 per year, thanks to the 4% rule. Retire…
Read guideHow Much Do You Need to Retire at 60?
Most people need $1.2 million to $2 million to retire at 60. The exact figure depends on your annual spending — multiply your yearly expe…
Read guideHow Much Do You Need to Retire at 65?
Most people need 25× their annual spending to retire at 65 — typically $1M–$1.5M. Social Security usually covers $20K–$35K per year on to…
Read guideThe 4% Rule Explained
The 4% rule says you can withdraw 4% of your starting portfolio in year one of retirement, adjust that dollar amount for inflation each y…
Read guideRoth IRA vs Traditional IRA: Which One Wins?
Pick a Roth IRA if you're young, in a low tax bracket, or expect higher taxes later. Pick a Traditional IRA if you're a high earner today…
Read guideWhat's the Best Age to Start Investing?
The best age to start investing is whatever age you are right now. Starting at 22 instead of 32 can roughly double your retirement balanc…
Read guideHow Much Will $300 a Month Grow To?
$300/month at a 7% return becomes about $52,000 in 10 years, $157,000 in 20 years, and $367,000 in 30 years. At 10% (long-term stock mark…
Read guideHow Much Will $5,000 Invested Grow To?
$5,000 invested once and left alone at a 7% return grows to about $9,800 in 10 years, $19,300 in 20 years, $38,000 in 30 years, and $75,0…
Read guideETF vs Mutual Fund Explained
For most long-term investors today, low-cost index ETFs win on fees, taxes, and flexibility. Mutual funds still make sense inside 401(k)s…
Read guideHow to Build Wealth in Your 20s
In your 20s, the formula is simple: build a 3-month emergency fund, capture every employer 401(k) match, invest 15–20% of income in low-c…
Read guideHow to Build Wealth in Your 30s
In your 30s, target a 20–25% savings rate, max your tax-advantaged accounts, lock in a 3–6 month emergency fund, avoid mortgage and lifes…
Read guideHow to Create a Savings Goal Plan (2026)
A complete savings goal plan answers four questions: how much, by when, in what account, and how much per month. Once you have those four…
Read guideHow Much Should You Save Each Month? (2026 Guide)
The standard recommendation is 20% of gross income — split roughly 10–15% into retirement and 5–10% into shorter-term savings goals. On a…
Read guideEmergency Fund Savings Guide (2026)
Most dual-income households should hold 3 months of essential expenses in a high-yield savings account. Single-income households, freelan…
Read guideMortgage & Affordability
Understand what you can really afford, plus deposits, rules of thumb, and mortgage mechanics.
How Much House Can I Afford? Complete Guide
Full beginner-to-advanced guide on home affordability, the 28/36 rule, and salary-based examples.
Read guideHow Much House Can I Afford by Salary
Affordability targets at $50K, $75K, $100K and beyond.
Read guideHow Much Should I Save for a House Deposit?
Realistic deposit targets, timelines, and where to keep the money.
Read guideBest Way to Save for a House
The accounts, automations, and tradeoffs that get you to a deposit fastest.
Read guideHow Much Is a $200K Mortgage Per Month?
Monthly payment ranges at common rates, terms, and PITI scenarios.
Read guide30-Year vs 15-Year Mortgage
Side-by-side payment, interest and equity comparisons.
Read guideMortgage Types Explained: Conventional, FHA, VA, USDA, Jumbo & ARM
Complete cornerstone guide to every major mortgage program — eligibility, down payment, PMI/MIP, pros and cons, and a decision framework.
Read guideThe 28/36 Rule Explained: How Lenders Decide What You Can Afford
Spend no more than 28% of your gross monthly income on housing (PITI), and no more than 36% on total debt payments (housing + car + stude…
Read guideHow Much Income Do You Need for a $300k House?
Most buyers need around $75K–$90K in household income to comfortably afford a $300K home with a 10% down payment at current rates (~6.5%)…
Read guideFHA vs Conventional Loan: Which Is Right for You?
Choose FHA if you have a lower credit score (under 680) or limited down payment (under 5%). Choose conventional if you have 5%+ down and…
Read guide5% vs 20% Down Payment: Which Is Better?
20% down avoids PMI, lowers your monthly cost, and saves tens of thousands of dollars in interest. 5% down lets you buy faster but costs…
Read guideHidden Costs of Buying a House
Plan for an extra 3–6% of the purchase price for closing costs upfront, plus 1–2% of home value annually for ongoing maintenance. On a $3…
Read guideHow Mortgage Amortization Works
Early in a mortgage, most of your payment goes to interest. By the final years, most goes to principal. On a $300K loan at 6.5%, year 1's…
Read guideFixed vs Adjustable Rate Mortgage (ARM)
Choose fixed-rate if you'll keep the loan more than 5–7 years or want predictability. Choose an ARM if you plan to move or refinance with…
Read guideWhat Credit Score Do You Need for a Mortgage?
Minimums: 580 for FHA, 620 for conventional, 580–620 for VA. Best rates start at 740+. Below 580 is very difficult.
Read guideHow Much House Can I Afford on $50k Salary?
$150K–$200K home price range. Monthly payment around $1,100–$1,400 (PITI). Requires roughly $15K–$25K in cash for down payment + closing…
Read guideHow Much House Can I Afford on $100k Salary?
$300K–$400K home price range comfortably. Monthly payment around $2,200–$2,800 (PITI). With 20% down and no other debts, you can stretch…
Read guideHow Much House Can I Afford on a $60K Salary?
On a $60K salary with moderate debts and a 10% down payment, most buyers can comfortably afford a home priced around $180,000–$240,000, w…
Read guideHow Much House Can I Afford on a $75K Salary?
On a $75K salary with moderate debts, most buyers can comfortably afford a home priced around $225,000–$300,000 with a typical 10% down p…
Read guideHow Much House Can I Afford on a $120K Salary?
On a $120K salary, most households can comfortably afford a home priced $360,000–$480,000 with moderate debt and a typical down payment.
Read guideMortgage Payment on a $400K House
With 20% down ($80K) on a $400K house at 6.5% over 30 years, the monthly principal & interest payment is about $2,022 — total monthly hou…
Read guideMortgage Payment on a $500K House
With 20% down ($100K) on a $500K house at 6.5% over 30 years, the monthly principal & interest payment is about $2,528 — full PITI usuall…
Read guideHow Much Income Do You Need for a $400K Mortgage?
To comfortably afford a $400,000 mortgage with the 28% rule, you typically need a household income of about $100,000–$120,000 per year —…
Read guideFHA Loan Requirements Explained
FHA loans require as little as 3.5% down with a 580+ credit score, a debt-to-income ratio under ~43%, two years of steady employment, and…
Read guideVA Loan vs Conventional Mortgage: Which Is Better?
For eligible veterans and active-duty service members, VA loans almost always win: 0% down, no PMI, and lower rates. Conventional loans o…
Read guideHow Much House Can I Afford on an $80K Salary?
On an $80K salary with a 10% down payment and average debts, most buyers can comfortably afford a home priced $240,000–$320,000, with mon…
Read guideHow Much Mortgage Can I Afford?
As a rule of thumb, your total monthly housing payment (PITI + HOA) should stay under 28% of gross monthly income, and total debts under…
Read guideHow Much Should You Spend on a House?
Most financial experts recommend spending no more than 2.5–3x your annual gross income on a house. On an $80K salary, that's a $200K–$240…
Read guideHow Much Down Payment Do You Need for a House?
Conventional loans allow as little as 3% down; FHA requires 3.5%; VA and USDA loans allow 0%. The classic 20% target only matters because…
Read guideHow Much House Can I Afford With 5% Down?
With 5% down, most buyers can afford a home priced 3–4× their gross annual income. On a $75K salary, that's roughly $250K–$300K — though…
Read guideHow Much House Can I Afford With 20% Down?
With 20% down, most buyers can comfortably afford a home priced 4–5× their gross income. On a $100K salary, that's roughly $400K–$500K wi…
Read guideMortgage Payment on a $300,000 House
The monthly payment on a $300,000 house typically runs $2,000–$2,400, including principal, interest, taxes, and insurance. The exact numb…
Read guideMortgage Payment on a $750,000 House
Monthly payment on a $750,000 house is typically $4,800–$5,500 with 20% down at today's rates. You'll generally need a household income o…
Read guideHow Much Will a $400K Mortgage Cost Per Month?
A $400,000 mortgage costs about $2,528 per month for principal and interest at a 6.5% rate over 30 years. Add property tax and insurance…
Read guideHow Much Will a $250K Mortgage Cost Per Month?
A $250,000 mortgage costs about $1,580 per month for principal and interest at a 6.5% rate over 30 years. With property tax and insurance…
Read guideHow Much Income Do You Need for a $500k House?
At a 7% mortgage rate with 20% down, you typically need a household income of about $125,000–$140,000 to comfortably afford a $500,000 ho…
Read guideHow Much Income Do You Need for a $750k House?
At a 7% rate with 20% down, you typically need a household income of about $190,000–$220,000 to comfortably afford a $750,000 house under…
Read guideIs It Better to Rent or Buy?
Buying usually wins financially if you stay in the home 5+ years and the price-to-rent ratio is below about 20. Renting usually wins if y…
Read guideHow Much Does Property Tax Cost?
The average U.S. property tax rate is about 1.1% of home value per year, but it ranges from 0.3% (Hawaii) to over 2.2% (New Jersey, Illin…
Read guideWhat Happens If Interest Rates Rise?
When interest rates rise, mortgage payments and credit card interest go up, house prices typically soften, and high-yield savings account…
Read guideLoans & Debt
Pay off loans faster, compare repayment strategies, and avoid expensive debt mistakes.
How to Calculate Interest on a Loan
Simple, compound, and amortized interest — with formulas and worked examples.
Read guideHow to Pay Off a Loan Faster
Proven extra-payment, biweekly, and refinance tactics with savings tables.
Read guideWhat Happens When You Make Extra Loan Payments?
On a $300,000 mortgage at 6.5% (30-year), an extra $200/month cuts the loan to about 24 years and saves around $80,000 in interest. Extra…
Read guideBiweekly vs Monthly Loan Payments
Biweekly payments mean 26 half-payments per year = 13 full monthly equivalents = one extra payment annually. On a $300K mortgage at 6.5%,…
Read guidePersonal Loan vs Credit Card Debt
If your credit card APR is above ~15% and you have decent credit, a personal loan usually saves money. But it only works if you stop usin…
Read guideHow Much Interest Will You Really Pay?
On a $300K mortgage at 6.5% over 30 years, you pay back ~$682,000. A $25K car loan at 8% costs ~$30,400. A $5K credit card balance at 24%…
Read guideAvalanche vs Snowball Debt Method
Avalanche pays the highest-interest debt first (saves the most money). Snowball pays the smallest balance first (builds momentum and moti…
Read guideHow to Pay Off Debt Faster
List all debts, attack the highest-interest first (or smallest balance for motivation), refinance high-rate debt where possible, and appl…
Read guideWhat Is Loan Amortization?
Amortization splits each fixed payment between interest (calculated on the remaining balance) and principal (the rest). Early payments ar…
Read guideEarly Loan Repayment Explained
Paying off high-interest loans (above ~7%) early almost always wins. For low-rate loans (mortgages under 5%, federal student loans), inve…
Read guideHow to Pay Off Credit Card Debt Faster (Step-by-Step)
The fastest, cheapest way to pay off credit card debt is the avalanche method: pay minimums on everything, then put all extra cash toward…
Read guideCar Loan vs Personal Loan: Which Is Cheaper?
Car loans are almost always cheaper than personal loans (rates 1–4% lower) because the car secures the loan. Use a personal loan only whe…
Read guideHow to Pay Off a Car Loan Early
The fastest way to pay off a car loan early is to add extra principal each month, switch to biweekly payments, or make one extra full pay…
Read guideDebt Payoff Plan Example (Real Walkthrough)
A solid debt payoff plan lists every balance, rate and minimum, picks a method (avalanche or snowball), commits a fixed monthly extra pay…
Read guideHow Loan Interest Really Works (Plain-English Guide)
Most loans charge interest on the remaining balance each month. Your fixed monthly payment first covers that month's interest, then anyth…
Read guideHow to Reduce Total Interest Paid on a Loan
The biggest interest savers: choose a shorter term (15-yr vs 30-yr can cut interest by 60%+), make extra principal payments, refinance wh…
Read guideMinimum Payment vs Extra Payment: What's the Real Difference?
On a $5,000 credit card at 22% APR, paying only the minimum (~2%) takes 25+ years and costs $11,000 in interest. Paying just $50 extra ea…
Read guideDebt Consolidation Explained: When It Helps (and When It Hurts)
Debt consolidation combines multiple debts into one payment, ideally at a lower rate. It works best when you have good credit, can qualif…
Read guideHow to Improve Your Credit Score Fast
The fastest credit score boost comes from paying down credit card balances below 10% of the limit, disputing inaccurate items, and becomi…
Read guideCredit Card Interest Explained
Credit card interest is calculated using a daily periodic rate (APR ÷ 365) applied to your average daily balance. If you pay your full st…
Read guideHow Long Will It Take to Pay Off Debt?
At a 20% APR, paying $200/month: $5,000 takes 33 months, $10,000 takes 95+ months. At $500/month: $5K is 12 months, $10K is 25 months, $2…
Read guideHow Much Debt Is Too Much?
A common benchmark: total debt payments (including housing) above 43% of gross income is 'too much.' Excluding mortgage, total consumer d…
Read guideReady to run the numbers?
Pair any guide with one of our free calculators to plan your next financial decision.
Frequently asked questions
Are CalcGrowth's financial guides free?
Yes. Every guide on CalcGrowth is free to read, with no signup, paywall, or affiliate sales pitch. The guides exist to make our calculators easier to use and to help readers make better financial decisions.
Who writes and reviews the guides?
Guides are written by the CalcGrowth editorial team and reviewed for accuracy before publication. Each guide focuses on the math, common trade-offs, and realistic example scenarios rather than generic advice.
Is the content on CalcGrowth financial advice?
No. CalcGrowth guides are educational. They explain how financial concepts work and how to use our calculators — they are not personalized investment, tax, or legal advice. For decisions about your specific situation, consult a qualified professional.
How often are the guides updated?
Each guide displays a 'Last updated' date. We refresh guides when interest-rate assumptions, tax thresholds, or best practices change materially, and we periodically review evergreen content for accuracy.
How do guides relate to the calculators?
Every guide is paired with at least one calculator so you can immediately model your own numbers. Guides explain the concept and worked examples; calculators let you run unlimited what-if scenarios with your real figures.