# $200/Month Extra on a $300k Mortgage — Mortgage Payoff Calculator

> Adding $200/month extra to a $300k 30-year mortgage at 6% saves $91,173 in interest and cuts the term by 6 years 9 months — a quarter of the loan gone.

- **Answer:** Save ~$91,173 in interest
- **Category:** Finance & Money
- **Interactive calculator:** https://youcalc.com/en/finance-money/mortgage-payoff/extra-200-per-month/
- **Price:** Free, no sign-up required
- **Full calculator:** [Mortgage Payoff Calculator](https://youcalc.com/en/finance-money/mortgage-payoff/)
- **Pre-filled inputs:** `m=known-term&p=300000&r=6&t=30&ry=30&rm=0&pk=extra-monthly&ea=200&c=USD`

| Metric | Value |
| --- | --- |
| Interest saved | $91,173 |
| Time saved | 6 yr 9 mo |
| New payoff term | 23 yr 3 mo |
| Monthly payment | $1,999 |
| Original term | 30 yr |


## Overview

An extra $200 a month on a $300,000 mortgage at 6% saves $91,173 in interest and retires the loan in 23 years 3 months instead of 30. That $91k represents more than 30% of the original principal returned to your pocket — not the bank. Double the extra payment from $100/month to $200/month and the interest savings nearly double too (from $53,347 to $91,173), confirming that extra-principal dollars are especially powerful early in the amortization schedule.

## Method

The calculation uses standard mortgage amortisation. The scheduled monthly payment is derived from the level-payment formula: P × r(1+r)^n / ((1+r)^n − 1), where P is the original principal, r the monthly interest rate (annual rate divided by 12), and n the total number of payments. From there, the calculator runs a month-by-month simulation: each period it applies the monthly rate to the current balance to find the interest charge, subtracts that from the payment (base plus any extra) to find the principal reduction, and carries the lower balance into the next period. Extra payments are added to the principal portion only, directly reducing the outstanding balance. The simulation stops when the balance reaches zero, and the total months elapsed becomes the new payoff term. Savings in interest and months are the difference between the no-extra simulation and the with-extra simulation, measured from the current period forward. The finance utilities supply the level-payment and balance-after-k-payments helpers used in the preliminary setup step.

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## Sources

- https://www.investopedia.com/mortgage-calculator-5096931
- https://www.calculator.net/mortgage-payoff-calculator.html

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Interactive version: https://youcalc.com/en/finance-money/mortgage-payoff/extra-200-per-month/ · From YouCalc — https://youcalc.com