Simple Interest Calculator
Compounding frequency (APR display only)
Effective annual rate: 5.000%
Total amount
$11,500.00
Interest earned: $1,500.00
- Interest earned
- $1,500.00
- Total amount
- $11,500.00
- Nominal APR
- 5.000%
- Effective annual rate
- 5.000%
- Estimated monthly payment
- $319.44
Simple division of the total by months — an estimate, not an amortization schedule.
Simple interest accrues on the original principal only — interest never earns interest.
Yearly breakdown
| Year | Start balance | End balance | Interest earned | Principal |
|---|---|---|---|---|
| 1 | $10,000.00 | $10,500.00 | $500.00 | $10,000.00 |
| 2 | $10,500.00 | $11,000.00 | $500.00 | $10,000.00 |
| 3 | $11,000.00 | $11,500.00 | $500.00 | $10,000.00 |
Simple Interest Calculator — Linear Interest, Total & APR
Simple interest is the straightforward kind: interest accrues on your original principal only, and earned interest never earns interest itself. This free calculator turns a principal, annual rate and term into the interest earned, the total amount, the effective APR for your chosen compounding frequency, and an estimated monthly payment — with a year-by-year breakdown where every row earns the identical amount.
Use it for short-term loans, late-fee estimates, or whenever a contract quotes simple interest. Compare frequencies to see the effective APR move while interest and total stay exactly fixed — proof that frequency here is display context only. Every calculation runs locally in your browser with no signup, and any scenario can be shared with a link that reproduces it exactly.
The simple-interest formula
One multiplication, no iteration: interest equals principal times rate times time. The total is principal plus interest, and the payment estimate divides the total by the number of months.
I = interest · P = principal · r = annual rate / 100 · t = years. The effective rate converts the nominal rate for the selected compounding frequency.
How it works
- Enter the principal — the original amount, from $0 to $10,000,000.
- Set the annual rate (0–25%) and the term in whole years (1–30).
- Pick a frequency to see the effective APR conversion — interest and total never change.
- Read interest, total, nominal and effective APR, the payment estimate, and the linear yearly breakdown.
Nominal vs effective APR
The same nominal rate converts to a higher effective rate with more frequent compounding: 12% monthly behaves like 12.683% effective. Frequency here is display context only — it never changes your interest or total.
Frequently asked questions
Why is every year identical?
Because simple interest accrues on the original principal only. Unlike compounding, earned interest never joins the base, so each year earns exactly P·r.
What does the frequency control do?
It converts the nominal APR to an effective annual rate for display. Your interest, total and payment estimate are computed from principal, rate and years alone.
Is the monthly payment exact?
It is a simple-division estimate (total divided by months), not a loan amortization schedule. Real installment loans amortize and behave differently.
What happens with a 0% rate?
Interest is zero and the total equals the principal exactly. The payment estimate divides the principal evenly across all months.
Does this include fees or taxes?
No — v1 models pure simple interest only. Fee-inclusive APR, taxes and compounding belong to other tools; treat results as the contract-math baseline.