How to use it
- Enter your starting amount and monthly deposit.
- Enter the annual rate and number of years.
- Press Calculate and compare interest earned with what you contributed.
Worked example
Starting with £1,000, saving £100 a month at 5% a year, compounded monthly for 10 years, gives £17,175.24 in total, from £13,000 contributed and £4,175.24 interest. The exact figure depends on whether deposits are made at the start or end of each month; this calculator treats the monthly deposit as made at the end of each month, and states that assumption on the page.
Formula, in simple words
Future value = starting amount × (1 + monthly rate)months + monthly deposit × (((1 + monthly rate)months − 1) ÷ monthly rate). Interest earns interest, which is why starting early matters more than a small rate difference.
Frequently asked questions
Is the return guaranteed? No. Rates change, and this is a planning estimate, not a promise of returns.
Does it include tax or inflation? No. Tax and inflation would reduce the real value, so treat the result as a before-tax, nominal figure.
Results are estimates for information only, not financial advice. Please check with a qualified adviser before making an investment decision.