Complete guide
Repayment Calculator: formula, worked example and interpretation
Estimate a fixed loan payment and show how an extra monthly amount changes payoff time and interest. Enter the known values and the result updates instantly with an auditable breakdown.
What the Repayment Calculator answers
Estimate a fixed loan payment and show how an extra monthly amount changes payoff time and interest.
Use the breakdown to compare the result with the source values before making a decision.
Formula and variables
The calculation uses scheduled payment=P×r/[1−(1+r)^−n]; extra reduces principal. Every variable comes directly from a labeled field.
scheduled payment=P×r/[1−(1+r)^−n]; extra reduces principalWorked example
A five-year $30,000 loan at 8% is compared with the same scheduled payment plus $100 monthly.
Changing any field recalculates the result immediately, so nearby scenarios can be compared without reloading the page.
How to use the result
Treat the result as a planning value and compare it with the detailed rows shown beside it.
Keep units and time periods consistent. Use the share or PDF action to preserve the exact assumptions.
Assumptions and scope
This assumes a fixed rate, no prepayment penalty and extra money applied directly to principal.
The calculator exposes its assumptions instead of filling missing facts with hidden estimates.
Accuracy checks
Confirm the units, dates, rates and source figures before relying on the output.
Round only the displayed answer; Calculator24 keeps full JavaScript precision for intermediate arithmetic and exported values.
Input and output checklist
| Item | What to enter or review |
|---|---|
| Inputs | Loan balance ($), APR (%), Remaining years, Extra monthly payment ($) |
| Equation | scheduled payment=P×r/[1−(1+r)^−n]; extra reduces principal |
| Example | A five-year $30,000 loan at 8% is compared with the same scheduled payment plus $100 monthly. |
| Limit | This assumes a fixed rate, no prepayment penalty and extra money applied directly to principal. |
Frequently asked questions
What does this Repayment Calculator calculate?
Estimate a fixed loan payment and show how an extra monthly amount changes payoff time and interest.
Which formula does it use?
scheduled payment=P×r/[1−(1+r)^−n]; extra reduces principal
Does the result update while I type?
Yes. Valid changes recalculate after a short delay and the previous result is not substituted for invalid input.
Which assumptions should I check?
Check units, rates, dates and every source value shown in the form.
Is the result exact?
This assumes a fixed rate, no prepayment penalty and extra money applied directly to principal.
Can I save or share the calculation?
Yes. Copy, Share, WhatsApp, PDF/Print, CSV, comparison and parameterized-link actions are available.
What to keep in mind
This assumes a fixed rate, no prepayment penalty and extra money applied directly to principal.
Results display up to 8 decimal places; exported numbers preserve calculation precision. This is a calculation summary, not an official certificate.