Savings Calculator
Free to use, with no sign up. Your entries stay in this browser; calculations run on your device.
Result
A = P(1 + r/n)^(nt) + Σ C(1 + r/n)^[n(t − tₖ)]; APY = 100[(1 + r/n)^n − 1]. P = principal, r = annual rate / 100, n = periods/year, C = each contribution, tₖ = its deposit time in years.
OpenStax Contemporary Mathematics: compound interest explains the principal formula. Contributions sum the same growth formula from each deposit time. Modeled APY assumes a constant nominal rate and equal compounding periods over one year. US Truth in Savings Act / Regulation DD, Appendix A: APY = 100[(1 + interest/principal)^(365/days) − 1]; the expression above is its one-year, fixed-rate specialization. Actual account disclosures can use different day counts and account terms.
Worked example: With $1,000 initially, $100 deposited at each month-end, 5% nominal interest compounded monthly and 2 years, the modeled balance is $3,623.53. Total contributed is $3,400 and interest is $223.53. With zero interest, $1,000 plus twelve monthly deposits of $100 is $2,200.
This is fixed-rate arithmetic. Amounts are USD; fees, withdrawals, changing returns, inflation and taxes are excluded. Money inputs accept up to two decimal places. Results round to cents without rounding intermediate interest. Monthly periods are 1/12 year and yearly periods are 1 year. Only complete contribution periods count: deposits occur at their start or end; a fractional tail earns modeled interest but has no partial deposit. Fractional compounding uses exponential interpolation. Zero years means no deposits or interest. The table includes every full year and any final fractional year.
Arithmetic only; not financial advice.
Underlying engine: Compound Interest Calculator. Related calculators: Investment Calculator, CD Calculator, Simple Interest Calculator.
How to use this tool
Enter your starting balance in USD, fixed nominal annual rate and term. Recurring deposits start at $100 monthly; choose deposit amount, frequency, timing and compounding, then Calculate.
Frequently asked questions
How are deposits included?
Only complete monthly or yearly contribution periods count. Choose deposits at the start or end of each period. A fractional tail earns interest without a partial deposit.
Can I use a zero interest rate?
Yes. The balance then equals the starting principal plus all completed recurring deposits. A zero-year term has no recurring deposits.
Does this find a savings target or bank rate?
No. It models the amounts and fixed rate you enter. It does not solve a target date, fetch bank rates or recommend an account.