How this calculator works
Interest is reinvested rather than withdrawn. Deposits occur at the end of each contribution period. When contribution and compounding frequencies differ, an equivalent periodic growth rate is used, including fractional compounding periods. This is a constant-rate projection without fees, taxes, inflation or market volatility.
The formula
Balance = P × (1 + r/n)^(nt) + C × ((1 + i)^k − 1) / i × residual growth
P = initial investment; r = annual rate / 100; n = compounds per year; C = deposit; i = equivalent deposit-period rate; k = completed deposit periods.
At zero interest: Balance = P + Ck.A quick example
Investing 1,000 at 10% compounded annually for 2 years, with a 100 deposit at each year end, produces 1,420: 1,200 in deposits and 220 in interest.
How to use this calculator
- Enter your initial investment and annual nominal rate.
- Choose years, compounding frequency and an end-of-period contribution schedule.
- Calculate and compare final balance, total deposits and interest.
A few common questions
Are contributions made at the start or end?
At the end of each completed contribution period. An incomplete final period receives no new deposit.
Is the rate an APY?
No. Enter a nominal annual rate. Compounding determines its effective annual growth rate.
Can I model no contributions?
Yes. Enter zero additional contribution to calculate growth of the initial investment alone.