Interest earned without compounding
The main result answers the selected calculation: interest, principal, annual rate or time in years. The breakdown also shows interest and the principal-plus-interest amount. Doubling time doubles interest when principal and rate stay fixed.
If earned interest is reinvested, the Compound Interest Calculator models interest on the growing balance and optional regular contributions.
The formula
The annual percentage is divided by 100. Months divide by twelve; days divide by the selected 360 or 365. Dates use actual elapsed UTC calendar days with an optional extra final day. Daily average divides interest by the equivalent days. Reverse results need nonzero known factors; a zero denominator does not identify a unique answer.
Worked example
On 10,000 at 5% a year for three years, interest is 1,500 and the combined amount is 11,500.
How to use this calculator
- Choose interest, principal, annual rate or time as the result to solve.
- Enter the other known values; reverse modes use the interest amount, excluding principal.
- For a known term, choose years, months, whole days or calendar dates. Select the day divisor and whether the final date adds a day.
Convert time to the same unit as the rate
The entered rate is annual, so twelve months correspond to one year and three months to 0.25 years. A daily or monthly quoted rate must first be converted to a comparable annual simple rate. Dividing an actual calendar interval by 365 can differ from a contract that uses another day-count convention.
Separate accrued interest from a repayment plan
This calculation holds the original principal constant. It does not reduce the interest base as installments are paid, and it does not add earned interest back to principal. For a repayment loan or a deposit that reinvests interest, use a model that matches those cash flows and compounding terms.
Solve a missing factor from earned interest
An interest amount of 1,500 at 5% over three years implies principal of 10,000. The same principal and interest imply a 5% annual rate over three years, or a three-year term at 5%. These reverse modes use interest alone, not the principal-plus-interest balance.
At 10,000 principal and 6% annual interest, 90 days gives 150 under a 360-day divisor. A 365-day divisor gives approximately 147.95. The selected convention must match the agreement before using the number as a payable amount.
Assumptions & limitations
What this calculation assumes
- Principal and annual simple rate remain fixed.
- Months are twelfths of a year; day and date entry uses the chosen fixed 360/365 divisor.
What to keep in mind
- No compounding is included.
- Payment schedules and fees are excluded.
- Actual products may use exact-day conventions.
Common questions
What is the difference from compound interest?
Simple interest never earns interest on earlier interest.
Can time be a decimal?
Yes. For example, 0.5 represents half a year.
What happens when time is zero?
Interest is zero and total equals principal.
Does 360 days mean the 30/360 convention?
No. Actual elapsed calendar days are counted, then divided by 360. Contractual 30/360 adjusts calendar dates and is not implemented.
Why can a zero known factor prevent reverse solving?
If principal, rate or time in the denominator is zero, the remaining unknown is not uniquely determined. Supply nonzero known factors or use forward interest mode.
Sources & further reading
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