Extra Payment Calculator
See how extra payments can save you thousands in interest and years off your mortgage. Even small additions to your monthly payment make a huge difference.
Current Loan
Extra Payments
You Save
in interest savings
Comparison
Quick Savings Scenarios
Popular extra payment strategies for your $300,000 loan at 6.71%
| Strategy | Interest Saved | Time Saved |
|---|---|---|
| +$100/mo | $-68,754,710 | - |
| +$200/mo | $-68,325,068 | - |
| +$500/mo | $-67,036,141 | - |
| +$1000/yr lump | $-68,838,714 | - |
| $5000 one-time | $-69,056,640 | - |
How to Calculate Extra Payment Savings
- Step 1: Enter your current loan details — input your loan amount, interest rate, and loan term. This establishes your baseline amortization schedule.
- Step 2: Enter your extra monthly payment — this is the additional amount you plan to pay each month above the minimum. Even $100/month makes a significant difference.
- Step 3: Add any extra yearly or one-time payments — you can model annual lump sums (e.g., tax refund) or a single one-time payment to see their impact.
- Step 4: Compare the quick savings scenarios — the table shows five popular strategies so you can see which approach fits your budget and goals best.
- Step 5: Review your total savings — check the interest saved, payoff time reduction, and the side-by-side comparison of total interest with and without extra payments.
What Is a Mortgage Extra Payment?
An extra mortgage payment is any amount you pay above your regular monthly payment. Even small additional payments reduce your principal balance faster, saving you thousands in interest and shortening your loan term significantly.
How Does the Extra Payment Calculator Work?
Our calculator compares your current loan amortization schedule with one that includes extra monthly, yearly, or one-time payments. It shows you exactly how much interest you save and how many years you knock off your mortgage.
Why Use Our Extra Payment Calculator?
- See the real dollar savings from different extra payment strategies
- Compare monthly extra payments, yearly lump sums, and one-time payments
- Find the optimal extra payment amount that fits your budget
Methodology & Assumptions
How this calculator works, what it assumes, and where it falls short. Every calculator on TruePITI documents its math.
Formula
- Extra payment model: each month, the extra amount pays down principal directly (not next month's payment). Interest savings = sum of interest avoided on the accelerated principal over the remaining term. Payoff shortens by solving for the month when balance reaches 0.
Assumptions
- Extra payments assumed every month at the entered amount — lump sums differ slightly.
- No prepayment penalty (true for most FHA/VA/conventional; check ARM and investment loans).
- Rate fixed for the modeled term.
Limitations
- Biweekly and extra-monthly strategies differ from monthly extra amounts — see the biweekly calculator for that comparison.
- Refinancing later resets the schedule and can erase early-payment gains.
- Lenders apply extra to principal only if you instruct them — otherwise it may sit as a credit.
Worked Example
- $300,000 at 6.625% for 30 years: base payment $1,921; adding $200/month saves about $77,000 in interest and pays off 7 years early.
Sources
- CFPB — Owning a home
- Standard amortization math (verified)