Compound Interest Calculator
Future value of savings with compound interest and optional monthly contributions.
Results
Future value
22,179.14
Amount
17,000.00
Interest earned
5179.14
Value in today's money
22,179.14
Real gain
5179.14
The dashed line marks the value you entered.
What this tool does
Compound interest pays interest on the interest already earned, which is why the curve bends upwards instead of rising in a straight line. Add a monthly contribution to see how regular saving changes the outcome — over long periods it usually matters more than the rate.
Formula
FV = P × (1 + r/n)^(n·t) + PMT × [((1 + r/n)^(n·t) − 1) ÷ (r/n)]
Variables
| Symbol | Meaning | Unit |
|---|---|---|
p | Principal | — |
r | Annual interest rate | % |
t | Years | — |
nn | Compounding periods per year | — |
pm | Monthly contribution | — |
inf | Annual inflation rate | % |
FV | Future value | — |
IN | Amount | — |
GA | Interest earned | — |
RV | Value in today's money | — |
RG | Real gain | — |
Worked example
- Principal5000
- Annual interest rate4 %
- Years10
- Compounding periods per year12
- Monthly contribution100
- Annual inflation rate0 %
- Future value22,179.14
- Amount17,000.00
- Interest earned5179.14
- Value in today's money22,179.14
- Real gain5179.14
Limitations
- This is an informational calculator, not personalised financial advice. Rates, fees, taxes and contract conditions vary between institutions and countries.
- The tool works with whatever currency you use for the inputs; it does not convert between currencies.
- The calculation runs at full precision and only the display is rounded. If you copy an intermediate value and retype it, small differences can appear.
Frequently asked questions
Does the compounding frequency really matter?
Less than most people expect. At 4 % over ten years, €5000 grows to €7401 with annual compounding and €7459 with monthly — a difference under 1 %. The rate and the time do the heavy lifting; the frequency is a detail unless the rate is very high.