Simple interest calculator
Interest calculated only on your original principal, never on interest already earned — the straight-line counterpart to compound interest.
Future value
$1,150.00
Total interest
$150.00
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Growth over time
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| Year | Start balance | Contributions | Interest earned | End balance |
|---|---|---|---|---|
| 1 | $1,000.00 | $0.00 | $50.00 | $1,050.00 |
| 2 | $1,000.00 | $0.00 | $50.00 | $1,100.00 |
| 3 | $1,000.00 | $0.00 | $50.00 | $1,150.00 |
How this is calculated
Simple interest is always calculated on your original principal, never on interest you've already earned — that's what makes it "simple": interest = principal × rate × time, a straight line instead of a curve. Compound interest (our compound interest calculator) reinvests the interest earned each period, so it grows faster the longer money is left in place. Simple interest is common for short-term loans and some certificates of deposit; compound interest is how most savings and investment accounts actually work.
This is an educational estimate, not financial advice.