Savings Calculator
See how your initial deposit and monthly contributions compound over time at a fixed annual interest rate.
Ending Balance
$30,941$
After 10 years of saving with compounded monthly interest
A savings calculator computes the future value of money when you start with an initial deposit and add fixed monthly contributions. It accounts for compound interest—where interest earned itself earns interest—compounded monthly, creating exponential growth over time. For example, £1,000 initially plus £200 monthly at 4% annual interest grows to £32,452 in 10 years, with £5,452 coming purely from interest.
The calculator takes your starting amount, monthly savings amount, annual interest rate, and investment period. It then applies the compound interest formula separately to both your initial lump sum and your recurring monthly contributions, adding them together to give you the final balance. It also splits the result into total amount deposited and interest earned so you see exactly how much of the growth came from your own savings versus investment returns.
FV = P(1 + r/n)^(nt) + PMT × [((1 + r/n)^(nt) − 1) / (r/n)]FV is the final value; P is the initial principal; PMT is the monthly payment; r is the annual interest rate as a decimal; n is the compounding frequency per year (12 for monthly); t is time in years.
| Input | Result | Notes |
|---|---|---|
| Initial £1,000, Monthly £200, Rate 4% p.a., Time 10 years | Ending Balance: £32,452 | Total Deposited: £25,000 | Interest Earned: £7,452 | Shows the power of consistent monthly savings: your contributions are modest, but 10 years of compounding adds £7,452 in pure interest. |
| Initial £5,000, Monthly £500, Rate 5% p.a., Time 15 years | Ending Balance: £121,687 | Total Deposited: £95,000 | Interest Earned: £26,687 | Higher contributions and longer time horizon: interest earned reaches 28% of the final balance, demonstrating accelerating returns over 15 years. |
| Initial £500, Monthly £100, Rate 3% p.a., Time 20 years | Ending Balance: £32,707 | Total Deposited: £24,500 | Interest Earned: £8,207 | Even modest deposits add up: 20 years of £100/month at just 3% accumulates to £32k, with a third of the growth pure interest. |
Compound interest means you earn interest on your interest. A £100 deposit earning 5% yields £5 in year one; in year two, that £5 also earns interest. Over decades, this exponential effect dominates: a £10,000 deposit at 5% grows to £25,937 in 20 years, with £15,937 coming purely from compounding.
UK savings accounts currently range 4–5.5%; high-yield accounts may offer 5–6%. Fixed-rate bonds offer 4–5.5%. ISAs (tax-free) typically match regular account rates. Use your account's stated rate or a conservative average if you're comparing options. The calculator shows you the impact of even 0.5% differences over 10+ years.
This calculator uses monthly compounding, which matches most UK savings accounts. Daily compounding (some premium accounts) yields slightly more (1–2% extra over 20 years), but the difference is modest. Monthly is standard and realistic for retail savings.
The calculator assumes perfectly regular monthly deposits. If you're irregular (e.g., you save £500 some months and £200 others), use the average monthly amount. The result will be approximate but directionally correct.
This tool assumes a constant rate over the entire period, which is unrealistic for real markets. Run multiple scenarios: one with a conservative low rate, one with your current rate, and one higher to see a range of outcomes. Real rates fluctuate; this calculator is a baseline, not a forecast.
Savings accounts offer security and consistent rates (currently 4–6%); investment funds offer higher growth potential (historically 7–10% annually) but with volatility and risk. This calculator works for either—plug in the rate you expect and see the outcomes. Conservative savers typically use accounts; long-term investors use funds.