Pay a little extra each month. How much sooner is it gone?
Everyone knows extra principal helps. Almost nobody knows how much, or that the first $50 a month is worth far more than the fifth. This template runs the whole amortisation once for every extra amount you want to compare, and puts payoff time and total interest side by side.
Personal Finance Starter Data Table free
After you install, this is the model to open.
How Much Sooner Does an Extra Payment End the Loan?
- In your spreadsheet, click the Sortia icon in the strip of icons down the right-hand edge. No strip? Click the arrow at the bottom-right to open it. You can also use Extensions, then Sortia, then Open Sortia.
- Click Start from a template and put that name in the search box.
- Pick the card with that name and click Load this template. It arrives on a new tab with real numbers already in it.
The answer
A $32,000 car loan at 6.9% over 72 months. The $0 row is your baseline, so read the rest against it:
- No extra
- 72 months
- +$100 / mo
- 59 months
- +$200 / mo
- 50 months
- Interest saved at +$200
- $2,304
The returns fade fast. The first $50 a month saves $763 in interest; going from $200 to $250 adds only about $350 more. That curve is invisible in any single-answer calculator, and it is the whole reason to see several amounts at once. The effect is far larger on a mortgage: on $400,000 at 6.5%, an extra $200 a month clears the loan 67 months early and saves $111,892 in interest. Change three cells and the same template tells you your number.
The model
A full month-by-month amortisation: interest accrues on the balance, your scheduled payment plus anything extra comes off it, and the loan ends the month the balance hits zero. The schedule runs 360 months, so the same model handles a car loan and a 30-year mortgage.
| Loan amount | $32,000 |
| Annual interest rate (APR) | 6.9% |
| Term (months) | 72 |
| Scheduled payment | $544.03 |
| Extra principal per month | varied by the table |
| Payoff (months) | calculated |
| Total interest paid | calculated |
Once it is in your sheet
- The model arrives with real numbers in it and runs as it stands, so you can press the button first and understand it second.
- Change the numbers to yours. The sheet marks which cells are inputs and which hold formulas, and most labels carry a note explaining the row.
- Press the run button at the bottom of the panel. It is labeled for the tool you are in, and the result lands on its own tab, with a written reading of it beside the figures.
Never used Google Sheets? Start here goes the whole way, in seven steps, and assumes nothing.
Next question
- Will you actually hit your savings goal?Will You Hit Your Savings Goal?
- Will your retirement money last to 95?Retirement: Will the Money Last?
- Should you buy the house or keep renting?Rent vs Buy a House
- Will this rental actually cash flow?Does the Rental Property Make Money Most Months?
- Which deductible really costs you less?Which Health Plan Costs Less Over a Year?
- Can you really afford six months off?Can I Afford a Sabbatical?
Every model like this one, and the method behind them: What-if analysis in Google Sheets.