Simple interest calculator with your own rate

Calculate simple interest and the final balance from your principal, rate and time period. Review the formula and steps using the rate you provide.

Processed in your browser: your data are not uploaded.

Set your data

Principal

Interest rate (%)

Rate period

Duration

Duration unit

Currency

Uses your entered rate, without compounding, installments, statutory rates, taxes or fees. A 360-day basis is not a date-based 30/360 convention.

Result

Enter your inputs and calculate.

Applied formula

We count which tools are used most, without including entered values or file contents in the statistics. Privacy

How to use the tool

Enter principal, rate and its period.
Choose duration in years, months or days with an explicit 365- or 360-day year.

Method and principles

I = C × (r / 100) × n; M = C + I.

Rate and duration must use matching periods.

For simple interest, annual rate divided by 12 gives the monthly rate.

Check the rate period and day basis.

A fixed-rate contract may compound interest: a fixed rate alone does not imply simple interest.

Formula

T = C \times (1 + \frac{r}{100} \times t)

Formula and limits

Uses your entered rate, without compounding, installments, statutory rates, taxes or fees. A 360-day basis is not a date-based 30/360 convention.

Example

1000 at 5% annually for 2 years earns 100 interest, giving 1100 total. With a 365-day basis, 182 days is 182/365 of a year.

Practical example

Input

Principal: 1000
Interest rate (%): 5
Rate period: Annual
Duration: 2
Duration unit: Years
Currency: USD

Result

$1,100.00

Calculation steps

Substitute the example values into the formula.
$T = 1000 \times (1 + \frac{5}{100} \times 2)$

I = C × (r / 100) × n; M = C + I. Rate and duration must use matching periods. For simple interest, annual rate divided by 12 gives the monthly rate.

Result details

Result details
Parameter	Value
Interest	$100.00
Principal	$1,000.00

Limits and checks

Limits and checks
Parameter	Value
Principal	≥ 0; ≤ 1000000000000
Interest rate (%)	≥ 0; ≤ 1000
Duration	≥ 0; ≤ 100000

Sources

B3 — Juros simples

Frequently asked questions

Does a fixed rate mean simple interest?

No. Fixed describes whether the rate changes; simple describes interest on the original principal. Check the contract’s interest model.

Where are my inputs processed?

Calculations run in your browser. Entered amounts are not sent to the server.