15 vs 30 Year Mortgage Calculator
Interest savings and monthly difference between 15 and 30 year mortgage terms
Compare 15-year versus 30-year mortgage showing interest savings and monthly payment difference. Enter loan amount and 15-year rate to size affordability.
What this tool does
This calculator models the financial trade-off between two common mortgage terms by comparing monthly payment obligations and total interest costs. Enter your loan amount and the interest rates available for each term, and the tool calculates your monthly payment under both scenarios, the total interest paid over the life of each loan, and how much interest you'd pay less with the shorter term. The monthly payment difference shows how much more (or less) you'd pay each month to accelerate repayment. The shorter term typically carries a higher monthly obligation but significantly lower total interest, while the longer term spreads payments over more months, reducing each payment but increasing cumulative interest. Results illustrate the mathematical relationship between term length, payment size, and total borrowing cost—useful for understanding trade-offs when evaluating mortgage options. This is educational modelling and doesn't account for tax treatment, fees, or other loan-specific conditions.
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Formula Used
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Disclaimer
Results are estimates for educational purposes only. They do not constitute financial advice. Consult a qualified professional before making financial decisions.
15-Year vs 30-Year Mortgage Trade-Off
15-year mortgages typically offer 0.5-1% lower interest rates than 30-year mortgages but require substantially higher monthly payments. The decision affects total interest paid dramatically: 30-year mortgage often pays 2-3x principal in total interest; 15-year often pays 40-60% of principal. Monthly payment typically 30-50% higher on 15-year term. The math heavily favors 15-year if monthly payment is affordable; 30-year provides flexibility at higher lifetime cost.
Typical Rate Differences
Current mortgage rates: 30-year fixed 6.0-7.0%, 15-year fixed 5.25-6.25%. Similar spread pattern. Rate difference typically 0.5-1.0% favoring 15-year. This rate advantage combined with shorter amortization dramatically reduces total interest. On 300,000 loan: 30-year at 6.25% pays 365,000 total interest. 15-year at 5.50% pays 141,000 total interest — 224,000 less. Monthly comparison: 30-year about 1,847. 15-year about 2,451. 604 higher monthly but interest savings 224,000 over lifespan.
Worked Example for Common Scenario
Loan 300,000. 15-year 5.5%. 30-year 6.25%. 15-year monthly 2,451. 30-year monthly 1,847. Monthly difference 604 more on 15-year. 15-year total interest 141,000. 30-year total interest 365,000. Interest saved 224,000. The borrower paying 604 more monthly saves 224,000 in lifetime interest plus builds equity dramatically faster. After 15 years, 15-year mortgage is fully paid; 30-year has 50% of balance remaining. Equity position dramatically different at same tenure point.
What the Calculator Does Not Model
Opportunity cost of extra monthly payment in 15-year scenario (could invest 604/month at market returns). Tax deductibility of mortgage interest (if applicable in your jurisdiction). Refinance opportunities that could change rate over time. Ability to make extra payments on 30-year reducing its effective term. Specific lender rate offerings varying from typical spread. The calculator shows basic interest comparison; comprehensive decision includes investment alternatives.
When Each Term applies
15-year advantages: massive interest savings, faster equity building, forced discipline, debt-free sooner. Best when comfortable with higher monthly payment. 30-year advantages: lower monthly payment provides flexibility for investments, unexpected expenses, lifestyle. Best when monthly cashflow is tight or you invest aggressively. Hybrid approach: take 30-year for flexibility but make 15-year-level payments when possible — captures most benefits with safety of lower required payment.
On $300,000 loan, 15-year at 5.5%% saves 223,749.51 vs 30-year.
Inputs
This example uses typical values for illustration. Adjust the inputs above to match a specific situation and see how the result changes.
Sources & Methodology
Methodology
The calculator computes monthly payments for both loan terms using the standard amortization formula, which accounts for the loan amount, interest rate, and term length. Total interest paid over the life of each loan is derived by multiplying the monthly payment by the number of months and subtracting the original principal. The interest savings figure represents the difference between total interest under the 30-year term and the 15-year term. The monthly payment difference shows how much more a borrower would pay each month by choosing the shorter term. The model assumes fixed interest rates throughout the loan period, treats rates as constant, and applies no fees, prepayment penalties, property taxes, insurance, or other borrowing costs. Results are estimates and do not account for changes in circumstances or early repayment scenarios.
References
Frequently Asked Questions
Which term to choose?
Can I pay off 30-year early?
What about opportunity cost of higher 15-year payment?
Is there a 20-year mortgage?
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