Compound interest on a single starting balance
Compound interest means that credited interest becomes part of the balance that earns subsequent interest. This page estimates the future value of one initial deposit at a constant annual rate. Choose principal, annual rate, years and compounding frequency. The result separates the final balance from interest earned and expresses that interest as a percentage of the starting balance. There is no monthly contribution field on this calculator; use the investment calculator when you want to model additional deposits.
Formula and rate convention
A = P × (1 + r / n)^(n × t). P is principal, r is the annual rate as a decimal, n is compounding periods per year and t is years. Daily means 365 periods, monthly 12, quarterly 4, half-yearly 2 and yearly 1. Interest earned is A − P; total growth is (A − P) / P × 100 when principal is positive.
The rate is treated as a nominal annual rate divided across the selected periods. An advertised APY or effective annual rate already includes compounding. Entering an APY and selecting monthly compounding would compound it again, so match your account's rate convention. Actual deposit accounts can also use daily accrual, different crediting dates and their own rounding rules.
What a projection does not promise
A constant rate is a scenario, not a guarantee of investment performance. Market returns vary, and a deposit rate may change. Taxes, platform fees, withdrawals and new contributions are excluded. Use a lower-rate scenario as well as your central assumption to see how sensitive the outcome is to the rate and time horizon.
The balance is nominal: it describes future currency units, not today's buying power. To compare purchasing power, divide the future balance by (1 + inflation rate)^years using a separate inflation assumption. Do not describe nominal interest as an inflation-adjusted profit. Changing the country's currency label does not exchange the starting amount or change the interest formula.
Worked examples
USD 10,000 at 6%, monthly, ten years
A = 10,000 × (1 + 0.06 / 12)^120 = USD 18,193.97. Interest is USD 8,193.97 and total growth is 81.9%, before tax and fees. This is a hypothetical constant rate.
Annual compounding comparison
The same starting amount at 6% compounded yearly reaches USD 17,908.48 after ten years. Monthly compounding adds about USD 285.49 under these assumptions; that difference is not another deposit.
GBP 5,000 at 4%, monthly for five years
Assume one deposit, no withdrawals, no extra deposits, no fees or tax and a constant nominal 4% annual rate. A = 5,000 × (1 + 0.04 / 12)^60 = GBP 6,104.98; interest is GBP 1,104.98. This is not a quoted UK savings rate or an AER. An effective annual rate already includes compounding; do not divide it by 12 and compound again.
PKR 100,000 at 8%, quarterly for three years
Assume a single starting balance and constant nominal rate, not a guaranteed local offer: 100,000 × (1 + 0.08 / 4)^12 = PKR 126,824.18. Interest is PKR 26,824.18 before taxes, fees or inflation. Currency selection changes labels, not the value of your starting balance.
Frequently asked questions
Can I add a monthly deposit?
Not on this page. The investment calculator models an initial balance plus regular monthly contributions.
Should I choose daily or monthly?
Choose the frequency and nominal rate that match your account terms. More frequent compounding at the same nominal positive rate increases the projected balance.
Is total growth an annual return?
No. It is total interest divided by initial principal over the whole selected term. It should not be compared directly with an annual rate.
Are taxes or withdrawals included?
No. The projection assumes the starting balance remains invested for the whole term without tax, fees or withdrawals.