Annuity payment calculator
The level payment and a month-by-month schedule of interest against principal.
Fill in the fields and the result will appear here automatically.
An annuity keeps the regular instalment fixed while its rate and term stay constant. Each row separates interest on the outstanding balance from principal repayment. Interest falls as the balance falls, but it need not dominate the first payment: the rate and term determine its share. This model uses a nominal annual rate divided into monthly periods and excludes fees and insurance.
How it works
Formula and logic
Monthly rate i = r/1200 and payment A = S·i/[1−(1+i)^−n]; at r = 0, A = S/n. The regular payment, monthly interest and principal are rounded to two decimal places. Interest is balance × i; the remainder pays principal. The last instalment equals its remaining balance plus interest. A payment that cannot reduce principal at this precision, or an unrepresentable result, produces a range message.
Example
A debt of 1,000,000 monetary units at 12% for 12 months gives 88,848.79 per month: first-month interest 10,000 and principal 78,848.79. The last instalment is 88,848.76 and total paid is 1,066,185.45. At 0%, a debt of 120,000 over 12 months gives 10,000 per month with no interest.
Fields and units
- Debt amount — $
- Rate — % yearly
- Term, months — months
How to use
- — Enter the debt and nominal annual percentage rate.
- — Choose a whole term from 1 to 480 months.
- — Compare first-month interest and principal with the regular instalment.
- — Inspect the final row, which settles rounding differences. Use one currency throughout.
Method and limitations
- Calculation method
- Formula and logic
- Data or methodology source
- Microsoft PMT: constant rate, equal payments and end-of-period timing
- Limitation
- Educational constant-rate model with month-end instalments. Actual payment dates, day-count conventions, fees, insurance and contractual rounding can change a lender’s schedule.
FAQ
How does this annuity schedule differ from the loan calculator?
It explains one repayment method month by month. Use the relevant loan model for an upfront fee, extra repayments or a comparison with equal-principal instalments.
Why does the last annuity instalment differ by a few cents?
Monthly rounding leaves a small adjustment. The last row settles it, so the displayed regular payment multiplied by the term can differ from the schedule total.
Does interest always dominate the first annuity instalment?
No. In the one-year example it is 10,000 out of 88,848.79. Its share depends on both rate and duration; the table supplies the actual split.
What does the annuity schedule show at a zero rate?
The debt is divided by the number of months. The last row absorbs any minor-unit rounding difference, and every interest entry is zero.