Interest Calculator
Gross interest, tax and net return at maturity
Free Simple Interest Calculator
The formula banks use for savings accounts and fixed deposits
This interest calculator multiplies your principal by the annual rate and the term to find gross interest with the simple interest formula, deducts tax if you enter a rate, and shows the net amount you will hold at maturity. Enter the term in days, months or years; the tax field is optional and set to zero by default. If interest is added to the principal and reinvested, use the compound interest calculator instead. Results are for information; the exact figure depends on your bank's day-count convention and local tax rules.
Features
Bank formula
Principal × rate × days ÷ 365
Tax aware
Gross, tax and net shown separately
Days, months, years
From a 30-day deposit to a 5-year bond
Private
Your amounts stay on your device
Formula and Examples
Simple interest
- Gross interest = Principal × Rate ÷ 100 × Days ÷ 365
- Net interest = Gross interest − Tax
- Example: 10,000 × 5% × 365 ÷ 365 = 500 per year
- Six months: 10,000 × 5% × 182 ÷ 365 = 249.32
Simple vs compound
- Simple: interest only on the original principal
- Compound: interest also on previously earned interest
- For terms under a year the difference is small
- Over many years compounding wins clearly
Frequently Asked Questions
How is simple interest calculated?
Multiply the principal by the annual rate and by the number of days, then divide by 365. For 10,000 at 5% over 90 days: 10,000 × 0.05 × 90 ÷ 365 = 123.29.
What is the difference between APR and APY?
APR is the simple annual rate used in this calculator; APY includes the effect of compounding within the year and is slightly higher for the same nominal rate.
Is interest taxed?
In many countries interest income is taxable, sometimes withheld at source. Enter your local rate in the tax field to see the net figure, or leave it at 0.
How much interest per month?
The 'net interest per month' box scales the net interest to a 30-day month, which is handy for comparing accounts with different terms.
Do banks use 360 or 365 days?
Most retail banks use 365 days; some markets use a 360-day convention. The difference is small but not zero, so check your bank's terms for exact figures.