15 vs 30 Year Mortgage Calculator

Compare the monthly payment, total interest, and total cost of a 15-year vs 30-year mortgage side by side.

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15-Year Mortgage
$2,572/mo
6.25% fixed · 180 payments
Total Interest
$163,008
Total Cost
$463,008
30-Year Mortgage
$1,946/mo
6.75% fixed · 360 payments
Total Interest
$400,486
Total Cost
$700,486
15-Year Advantage
Interest Saved
$237,478
Higher Monthly Payment
+$626/mo
Paid Off Sooner
15 years earlier
Total Savings
$237,478

How to Use This 15 vs 30 Year Calculator

Enter your Loan Amount and set separate rates for each term. Rates typically differ — 15-year mortgages usually carry rates 0.5–0.75% lower than 30-year. This rate difference is built into the default values but you can adjust both to match quotes you've received.

The two result cards show both scenarios simultaneously. The green savings panel below summarizes the key tradeoffs: how much more per month the 15-year costs versus how much total interest you save.

The Math Behind the Comparison

Monthly Payment = P × [r(1+r)^n] / [(1+r)^n - 1]

15-Year: n = 180 months
30-Year: n = 360 months

Total Interest = (Monthly Payment × n) − Principal
Total Cost = Principal + Total Interest

For a $300,000 loan: At 6.25% (15-yr), payment = $2,572 and total interest = $162,960. At 6.75% (30-yr), payment = $1,946 and total interest = $400,560. The 15-year costs $626 more per month but saves $237,600 in total interest — and builds equity twice as fast.

Example: The Tradeoff Decision

Two Paths to the Same $300,000 Home

15-Year at 6.25%30-Year at 6.75%
Monthly Payment$2,572$1,946
Monthly Difference+$626—
Total Payments$462,960$700,560
Total Interest$162,960$400,560
Interest Saved$237,600—
Paid Off15 years30 years
Equity at Year 10~$210,000~$120,000

The 15-year borrower pays $626 more per month but owns the home outright 15 years earlier and saves nearly a quarter million dollars in interest. The 30-year borrower has better monthly cash flow, which they could invest — but they'd need to consistently earn 6.75%+ to match the mortgage savings.

Frequently Asked Questions

For a $300,000 loan, a 15-year at 6.25% costs about $2,572/month vs. a 30-year at 6.75% costing $1,946/month — about $626 more per month (32% higher). However, the 15-year saves over $237,000 in total interest. Use the calculator with your specific numbers.
Not always. If you consistently invest the payment difference and earn returns above your mortgage rate, the 30-year with investing builds more total wealth. But "consistently investing the difference" requires discipline most people don't sustain. The 15-year is a forced savings plan with a guaranteed return equal to your interest rate.
Lenders face less risk with shorter loans: the borrower carries less total debt, is less exposed to interest rate changes, and has a shorter period in which to default. This lower risk profile allows lenders to offer rates typically 0.5–0.75% below 30-year rates.
Yes — take a 30-year but pay the equivalent of a 15-year payment. You get payment flexibility (drop to the minimum if needed) while paying off in roughly 15 years. The downside: you won't get the 0.5–0.75% rate discount of a true 15-year product, and discipline is required to maintain the higher payments.
Choose 30-year when: (1) You need lower payment for cash flow. (2) Your income is variable or commission-based. (3) You have high-interest debt to pay first. (4) You're buying in a high-cost market and need to qualify. (5) You're an active investor who will consistently deploy the payment difference at higher returns. Most first-time buyers benefit from 30-year flexibility.

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