15-Year vs 30-Year Mortgage Calculator
A 30-year mortgage looks $700 cheaper a month. Over the full term, it can cost an extra $200k in interest. See your exact numbers side-by-side.
About this tool
A side-by-side comparison calculator for the most consequential mortgage decision: term length. A 15-year mortgage carries a 0.5–0.75% lower rate but a 50% higher monthly payment than a 30-year. See the monthly cashflow gap, the lifetime interest gap, and the break-even on a 30-year-with-extra-principal strategy.
How to use it
Quick steps to get the most out of this utility.
- 1
Enter loan amount
Use the same principal for both scenarios — that is what makes the comparison fair.
- 2
Set the two rates
Typical spread: 15-year mortgages run 0.5–0.75% below 30-year rates. Use today's quotes from your lender for both.
- 3
Compare the totals
Monthly payment, total interest paid, and final payoff date for each term.
- 4
Run the hybrid
Optional: model "30-year mortgage + the 15-year monthly extra as principal payment." Often nearly matches the 15-year math with more flexibility.
- 5
Export the comparison
Download both schedules to share with your spouse or lender.
The honest framework for choosing
The 15-vs-30 debate is usually framed as math. It is actually a question about behavior, cashflow, and personality. The math is clear: 15-year saves a lot of interest. The behavior is the harder part — can you maintain a higher mandatory payment for 15 years through job changes, kids, or a recession?
Pick 15 if...
- You can comfortably afford the higher payment with 30%+ slack in your monthly budget.
- You are already maxing tax-advantaged retirement accounts (401k, IRA).
- You value the psychological certainty of being mortgage-free in 15 years.
- You suspect you would not actually invest the difference if you took a 30-year.
Pick 30 if...
- The 15-year payment leaves less than 20% slack in your budget.
- You have room to invest in tax-advantaged accounts but haven't yet.
- Your career is volatile (commission, freelance, startup equity).
- You will genuinely use the cashflow flexibility — and have evidence of past discipline.
Frequently asked questions
Is a 15-year or 30-year mortgage better?+
Depends on cashflow, discipline, and opportunity cost. The 15-year saves dramatically more interest and builds equity twice as fast, but the monthly payment is 40–50% higher. The 30-year frees cashflow for investment, retirement contributions, and emergencies — useful if you can earn more on those dollars than the mortgage rate costs. Most disciplined investors do better with a 30-year + maxing tax-advantaged accounts; most undisciplined ones do better being forced into a 15-year.
How much extra interest does a 30-year mortgage cost?+
On a $400k mortgage at typical 2024–2025 rates (15-yr at 6%, 30-yr at 6.75%), the 30-year costs roughly $935k total versus $608k for the 15-year — about $325k more in interest. That is $11k/year on average. The gap shrinks if you make extra principal payments on the 30-year, and grows if rates rise.
Why is the 15-year rate lower?+
Lender risk is lower. With a 15-year, the bank gets its principal back in half the time, so they are exposed to less default risk, less interest-rate risk, and less inflation risk on the locked-in rate. They share that saved risk back as a lower rate — typically 50–75 basis points lower than the 30-year equivalent.
Should I take a 30-year and just pay it off in 15?+
A common DIY strategy. Take the 30-year (lower payment, more flexibility) and voluntarily pay the 15-year equivalent monthly. You give up roughly 0.5% in rate but keep the option to drop back to the 30-year payment in any month you need cashflow flexibility. Mathematically, the 15-year still wins on total cost by ~$30–60k on a $400k loan — but the optionality is worth real money to most households.
Are there other mortgage terms besides 15 and 30 years?+
Yes. 10-year (rare, very aggressive amortization), 20-year (middle ground, ~25 bp below 30-year), 25-year (uncommon in the US, common in Canada), and 40-year (rare, mostly used in loan modifications). For most buyers, 15 and 30 are the only options worth comparing seriously — the others optimize for niche cases.
Keep exploring
More utilities and reading from Toolisk.
More views of the same calculator
Open main calculator →Same underlying engine, written for different use cases. Pick the angle that matches your situation.