Savings calculator
See how your savings could grow with interest and regular deposits.
Project your savings balance and interest from a lump sum and monthly deposits. Choose deposit timing, annual contribution increases and a savings target, and optionally see the final balance in today’s money.
See your savings grow
Example figures. Enter your details to build your savings plan.
Balance & money paid in
Hover or tap the graph to explore. Keyboard: arrow keys, Home and End.
The gap between the lines is interest earned. Figures are before tax and fees; interest is kept in the account.
Your £20,000.00 target
Not reached within 5 years. You would be £5,547.54 short.
- Starting monthly deposit needed to reach it by the end
- £283.83
Uses the same starting balance, AER, deposit timing and annual deposit increase. Target checks use end-of-month balances. The required deposit is rounded up to the next penny; this is not an affordability assessment.
- Starting balance
- £1,000.00
- Additional deposits
- £12,000.00
- Assumed AER
- 4%
This is a gross illustration, not a guaranteed return or a tax calculation. No account limits, withdrawals or rate changes are included.
View savings breakdown
| Month | Total paid in | Interest earned | Balance |
|---|---|---|---|
| 0 | £1,000.00 | £0.00 | £1,000.00 |
| 12 | £3,400.00 | £83.69 | £3,483.69 |
| 24 | £5,800.00 | £266.72 | £6,066.72 |
| 36 | £8,200.00 | £553.08 | £8,753.08 |
| 48 | £10,600.00 | £946.89 | £11,546.89 |
| 60 | £13,000.00 | £1,452.46 | £14,452.46 |
How this savings estimate works
AER expresses an annual return allowing for compounding. We convert it to an equivalent monthly rate: (1 + AER ÷ 100)^(1 ÷ 12) − 1. Interest stays in the account. This smooth monthly model does not reproduce a bank’s daily interest calculation or actual interest-crediting dates. Halifax explains AER and compound interest.
Each monthly deposit is added either before or after that month’s interest. Annual deposit increases begin in month 13, then month 25, and so on. Later deposits earn interest for less time, so applying the AER to all the money you pay in over a year would overstate the interest. Account-specific deposit caps, introductory rates and maturity terms are not modelled. See MoneyHelper’s regular savings guidance.
For inflation, we divide the future balance by (1 + inflation ÷ 100)^(months ÷ 12). This illustrates purchasing power, not a deduction from your account. See the Bank of England’s explanation of inflation and buying power.
What about tax and cash ISAs?
Results are before tax. Interest within an ISA is tax-free, but this tool does not check ISA eligibility or subscription limits. Outside an ISA, savings interest may be covered by unused Personal Allowance, the starting rate for savings or the Personal Savings Allowance. Your other income and interest matter, so we do not apply a flat tax deduction. Check HMRC’s savings interest rules for your circumstances.
Sources checked 7 September 2026. Rates and inflation entered here are assumptions, not product recommendations. Figures use unrounded calculations; actual provider statements may differ.
Calculation method
Future balance = P × (1 + r)ⁿ + C × ((1 + r)ⁿ − 1) ÷ r
This formula applies to a constant monthly deposit C made at month-end, with starting balance P and n months. The monthly rate r is (1 + AER ÷ 100)^(1 ÷ 12) − 1. For start-of-month deposits, multiply the contribution-growth term by (1 + r). At 0%, simply add the deposits to the starting balance. When annual deposit increases are selected, we calculate each month separately, increasing the deposit after every 12 months.
Worked example
Start with £1,000 and add £100 each month for two years at 0% interest: the final balance is £3,400. Separately, £10,000 left untouched at a constant 10% effective annual rate for two years becomes £12,100. These are mathematical examples, not available savings offers.
Method documented: · How we check calculations · Report an error
Common questions
What does AER mean in this calculator?
It is the effective annual rate, including the effect of compounding over a year. The calculator converts it to an equivalent monthly rate rather than simply dividing it by twelve.
Does the result include tax on savings interest?
No. The balance and interest are before tax and fees. Your net interest depends on the account, allowances and other income. The optional inflation figure separately shows purchasing power; it is not tax or an account charge.
What if my savings rate changes?
This version uses one constant AER. Compare scenarios with different rates, and check account conditions such as introductory bonuses, deposit limits and withdrawal restrictions.
How much do I need to save each month to reach my target?
Enter a target and a duration. The result works out a starting monthly deposit using your initial balance, AER, deposit timing and selected annual deposit increase. It rounds that deposit up to the next penny. The target is in future pounds and is not automatically adjusted for inflation.
Does this work for a regular savings account or cash ISA?
It can illustrate growth, but it does not enforce account deposit caps, maturity dates, ISA subscription limits or eligibility. Actual daily interest and payment dates can differ from our monthly model. Later deposits earn interest for less time than money saved at the start.