Compound interest calculator
United Kingdom / GBP. Plan deposits, fees, withdrawals and savings targets with the rate convention you choose.
Calculated in your browser. No account or email needed.
This release offers generic savings and loan planning in GBP. UK income tax, National Insurance, ISA allowances and UK mortgage rules are not modelled.
Your savings
MonthlyFirst-year deposit, added at the end of each month.
Effective annual rate (APY/AER), converted to an equivalent monthly rate.
Fees, contributions & inflation
Modelled as 1/12 of this percentage, deducted from the balance monthly. Avoid double-counting fees already in your rate.
Raises the monthly deposit after each complete year. Set 0% to keep deposits fixed.
Only changes the purchasing-power estimate, not the growth path.
Lump sums and withdrawals
Month 1 is the first projected month. Uses the selected start/end deposit timing.
Withdrawals happen at month end, after growth, fees and deposits. No borrowing is assumed if funds run short.
Change the rate assumption
Work toward a target
Future value after modelled withdrawals and fees. Set 0 to turn off the target illustration.
See what time could do
Assumptions£127,984.10 GBP
Your money over time
Projected balance (GBP)Deposits arrive at month end and regular contributions increase 0% each year. The entered rate stays constant. Total withdrawn: £0.00. Fees deducted: £0.00. The dashed line shows total deposits, with no withdrawals subtracted. Returns can be negative. Taxes and account limits are excluded.
Keep a plan. Try a what-if.
Save a comparison, then change your numbers. Inputs stay in this browser.
The longer view
Year-by-year growth
| Year | Total contributed | Total withdrawn | Total growth or loss | Projected balance |
|---|---|---|---|---|
| 1 | £13,000.00 | £0.00 | £568.14 | £13,568.14 |
| 2 | £16,000.00 | £0.00 | £1,314.70 | £17,314.70 |
| 3 | £19,000.00 | £0.00 | £2,248.58 | £21,248.58 |
| 4 | £22,000.00 | £0.00 | £3,379.15 | £25,379.15 |
| 5 | £25,000.00 | £0.00 | £4,716.25 | £29,716.25 |
| 6 | £28,000.00 | £0.00 | £6,270.21 | £34,270.21 |
| 7 | £31,000.00 | £0.00 | £8,051.86 | £39,051.86 |
| 8 | £34,000.00 | £0.00 | £10,072.60 | £44,072.60 |
| 9 | £37,000.00 | £0.00 | £12,344.37 | £49,344.37 |
| 10 | £40,000.00 | £0.00 | £14,879.74 | £54,879.74 |
| 11 | £43,000.00 | £0.00 | £17,691.87 | £60,691.87 |
| 12 | £46,000.00 | £0.00 | £20,794.61 | £66,794.61 |
| 13 | £49,000.00 | £0.00 | £24,202.48 | £73,202.48 |
| 14 | £52,000.00 | £0.00 | £27,930.75 | £79,930.75 |
| 15 | £55,000.00 | £0.00 | £31,995.43 | £86,995.43 |
| 16 | £58,000.00 | £0.00 | £36,413.35 | £94,413.35 |
| 17 | £61,000.00 | £0.00 | £41,202.16 | £102,202.16 |
| 18 | £64,000.00 | £0.00 | £46,380.41 | £110,380.41 |
| 19 | £67,000.00 | £0.00 | £51,967.58 | £118,967.58 |
| 20 | £70,000.00 | £0.00 | £57,984.10 | £127,984.10 |
Exported files contain financial inputs. Store and share them carefully. Printing includes your current plan and any loaded comparison.
How does this GBP savings projection work?
The projection uses GBP and monthly cash flows. Effective annual rates are converted to an equivalent monthly rate; nominal annual rates are divided by 12. You can add fees, rising deposits, lump sums, withdrawals and a second rate stage. Taxes and account-specific rules are excluded.
Reviewed October 23, 2026 by DollarMath. Educational estimates. Sources and calculation scope.
Common questions
What is available for United Kingdom?
This release offers generic savings and loan planning in GBP. UK income tax, National Insurance, ISA allowances and UK mortgage rules are not modelled.
Can I enter APY or AER?
Yes. Select Effective annual (APY / AER), which converts the entered annual rate to an equivalent monthly rate. Choose nominal only if your rate is quoted before compounding. Do not enter a separate fee already included in the rate.
Are saved plans converted when I switch currencies?
No. GBP comparisons are saved separately from other regions. Changing regions does not convert balances or reuse another currency’s saved plan. Calculations run in the browser, without requiring an account.
Are monthly contributions added at the start or end of the month?
The default is month end, after growth and fees. In the advanced settings, choose start of month to add each deposit before growth and fees instead. An optional annual increase raises the monthly deposit after every complete year.
Is the projected growth a guaranteed investment return?
No. The rates are your assumptions, held constant within each selected stage. Actual returns vary and can be negative. The main balance is in future currency amounts before tax and after modelled fees; the separate purchasing-power estimate uses your annual inflation assumption.
How are investment fees included?
The annual percentage fee is divided by 12 and deducted monthly from the balance after growth, before any month-end deposit. Total fees deducted exclude the additional growth lost because those fees are no longer invested. Enter a before-fee rate if you model a separate fee. Fixed charges, trading fees and taxes are excluded.
Can this calculate how much I need to save each month?
Yes. Enter a target final balance in the advanced settings. The illustration finds a first-year monthly contribution, to the cent, that reaches the target and funds requested withdrawals under your selected rates, fees, timing, lump sum and annual contribution increases. The target is in future currency amounts, and the result is not guaranteed.
What happens if planned withdrawals exceed available savings?
The projection withdraws only available whole cents and shows the first month with an unfunded withdrawal and the total shortfall. It does not assume borrowing. Withdrawn money is included when calculating growth, so a withdrawal is not counted as an investment loss.
Know the assumptions.
United Kingdom / GBP. Calculation version monthly-growth-v3. Sources reviewed October 23, 2026.
Monthly cash flows, with an explicit annual rate
Effective annual rates, such as APY or AER, use monthly rate = (1 + annual rate)^(1/12) − 1. A nominal annual rate instead uses annual rate / 12. For example, £10,000 at a 10% effective annual rate becomes £12,100 after two years without deposits, withdrawals or fees. These conventions are different, so check the rate on your account or investment illustration.
Deposits can arrive at month start or month end. An annual increase changes the recurring monthly deposit after each full year. A one-time deposit follows the same timing choice. The annual fee percentage is divided by 12 and deducted after monthly growth, before month-end deposits. Avoid charging a fee separately if it is already included in the rate you entered.
Withdrawals, staged rates and targets
Withdrawals happen at month end after growth, fees and deposits. They are capped at available whole cents, with unmet amounts reported separately. Growth equals final balance plus actual withdrawals minus total deposits. The dashed line shows total deposits without subtracting withdrawals; chart lines connect annual observations. A second rate starts after the chosen full year. Neither rate is a forecast.
The target illustration searches for a first-year monthly contribution, to the cent, up to £100,000. It uses your entered cash flows and requires all requested withdrawals to be funded. The target is in future currency amounts. Inflation separately discounts the final balance by (1 + inflation)^years. Calculations retain unrounded growth, round deposits to cents, and report annual balances to cents.
Regional scope
This release offers generic savings and loan planning in GBP. UK income tax, National Insurance, ISA allowances and UK mortgage rules are not modelled. These are generic educational models, not account-specific outcomes, legal eligibility checks or lender quotes. Dates are equal periods rather than actual calendar schedules. There are no account allowance, savings-tax, withdrawal-tax or benefit calculations. Investment returns can be negative.
Saved comparisons are separate for each region. No currency conversion is performed. Calculator inputs are not added to URLs, Analytics or advertising requests.