How it works
Choose installment savings to pay in every month, or a deposit to pay in once. Interest is simple, and tax is deducted from the interest at the rate you enter.
Total = principal + interest − tax
The formulas
- Installment interest = amount × (rate ÷ 12) × n(n+1) ÷ 2
- Deposit interest = amount × (rate ÷ 12) × months
- Tax = interest × tax rate
Standards and sources
- Simple interest, as most savings accounts use
- Tax rates and rules vary by country and product
- For reference only; check your bank's terms
Last reviewed October 8, 2026
Frequently asked questions
How is installment interest calculated?
Each monthly deposit earns simple interest for the months it stays in the account. With n deposits the total is amount × (rate ÷ 12) × n(n+1) ÷ 2.
What is the difference from a deposit?
Installment savings pay in every month and build up interest month by month. A lump-sum deposit pays in once and earns interest on the full amount for the whole term.
Is tax included?
Yes. Tax is deducted from the interest at the rate you enter, so the maturity amount shows the interest after tax. Rates differ by country and product.