How Much Interest Will You Really Pay?

Mortgage: the biggest interest bill of your life

• $300K @ 6.5%, 30-yr: pay $1,896/mo × 360 = $682,560 total. Interest: ~$382,560.
• $300K @ 6.5%, 15-yr: pay $2,613/mo × 180 = $470,340 total. Interest: ~$170,340 (saves $212K).
• $300K @ 5.5%, 30-yr: pay $1,703/mo × 360 = $613,080 total. Interest: ~$313,080.

Even a 1% rate change saves over $70K. Term length matters even more — the 15-year saves over $200K despite a higher monthly payment.

Car loans

• $25K @ 8%, 5-yr: $507/mo, total $30,415. Interest: $5,415.
• $25K @ 8%, 7-yr: $390/mo, total $32,734. Interest: $7,734.
• $50K @ 8%, 7-yr: $779/mo, total $65,468. Interest: $15,468.

Longer car loans look cheaper monthly but cost much more — and you owe more than the car is worth for years.

Credit cards (the most expensive)

• $5,000 @ 24%, paying $125/min: 6+ years, ~$3,800 interest.
• $5,000 @ 24%, paying minimum 2%: 15+ years, ~$11,000+ interest.
• $5,000 @ 24%, paying $300/mo: ~20 months, ~$1,140 interest.

Minimum payments are a trap. Doubling or tripling them cuts the interest cost by 60–90%.

Student loans

• $30K @ 6%, 10-yr standard: $333/mo, total $39,966. Interest: $9,966.
• $30K @ 6%, 25-yr extended: $193/mo, total $57,961. Interest: $27,961.

Income-driven repayment plans can ease cash flow but often increase total interest paid significantly.

Use the calculator

Frequently Asked Questions