Interest Calculators
Simple Interest Calculator
Calculate simple interest, where interest is charged only on the original amount and never on interest already accrued.
Total interest
$1,500
- Final amount
- $11,500
- Interest per year
- $500
How this calculator works
I = P × r × t
- P
- the principal
- r
- the annual rate as a decimal
- t
- the time in years
Example calculation
Illustrative example — not advice
Worked example — the simple interest calculator as it loads, using the default figures below.
- 01Enter principal: $10,000.
- 02Enter annual rate: 5%.
- 03Enter time: 3 years.
- 04Read the total interest from the results panel: $1,500.
Total interest: $1,500. Final amount: $11,500. Interest per year: $500.
These figures come straight from the calculator above running on the values listed, so you can retype them and confirm every number yourself. Change any input and the results update immediately. Illustrative only — not a quote, offer or recommendation.
Important considerations
- Most consumer borrowing compounds instead, which costs more.
- Part years are treated proportionally.
Related calculators
- Compound Interest CalculatorProject the growth of a balance with compounding and regular contributions.
- Loan Interest CalculatorTotal interest cost across the life of a loan.
- Effective Interest Rate CalculatorEffective annual rate for any compounding frequency.
- Future Value CalculatorWhat a sum today is worth in the future.
- Mortgage CalculatorEstimate your total monthly mortgage payment and see the amortisation schedule.
- Loan Payment CalculatorMonthly repayment, total interest and the effect of paying extra each month.
Terms used here
Frequently asked questions
Where is simple interest actually used?
Short-term notes, some car finance and many bonds pay simple interest on the face amount.
Disclaimer
Legamoney calculators are educational tools. Results are estimates based on the figures you enter and do not constitute financial, tax or legal advice.
Last reviewed 2026-08-01