Savings goal calculator
This calculator answers one of two questions: how long a target takes to reach at a chosen monthly amount, or what monthly amount reaches a target by a chosen date. Both estimates include interest at the entered rate, held constant for the whole period, an assumption real accounts do not guarantee.
A savings goal calculator estimates how long it takes to reach a target amount by compounding monthly deposits at a given interest rate, or works backwards from a deadline to find the monthly amount required. Saving £200 per month at 4.5% interest from zero takes approximately 7 years and 4 months to reach £20,000, of which about £2,800 is interest earned. Enter a target below to calculate a timeline and milestones.
What are the milestones along the way?
| Milestone | Amount | Time from now | Reached by |
|---|---|---|---|
| 25% of target | £5,000 | 5 months | February 2027 |
| 50% of target | £10,000 | 1 year 5 months | February 2028 |
| 75% of target | £15,000 | 2 years 4 months | January 2029 |
| Target reached | £20,000 | 3 years 3 months | December 2029 |
Milestone dates use the plan the calculator is currently showing, so they follow the monthly figure in the answer above rather than a separate assumption.
How is the savings goal figure worked out?
Both answers come from the same one-line sum. Each month the balance is multiplied by a growth factor, then your payment is added. Written out: new balance equals old balance times g, plus the monthly payment. The g is the monthly growth factor, which comes from the annual rate. A 4% account paying interest monthly grows by about 0.327% a month, so g is 1.00327.
To answer how long will it take, the calculator simply runs that line forward, one month at a time, and stops at the first month where the balance reaches your target. There is no clever formula involved, and stepping through month by month is what makes it possible to say which month each milestone falls in.
To answer how much per month, the same relationship is turned inside out. After n months the balance is the starting amount grown for n months, plus every payment grown for however long it has been sitting there:
balance = saved x gn + monthly x (gn minus 1) divided by (g minus 1)
Set the balance to your target, then rearrange for the monthly figure. The starting amount is grown forward first, that result is taken off the target, and what is left is divided by the annuity factor, which is the second bracket above. If the rate is 0% the maths collapses to something simpler: the target minus what you have, divided by the number of months. If your starting amount alone would already grow past the target, the required payment is zero and the calculator says so.
Payments are treated as arriving at the end of each month, which is the cautious assumption. Interest earned is the balance minus everything you put in, so the three blocks on the bar above always add up to the balance.
What does a worked example look like?
Take a target of £20,000 with £3,000 already saved, adding £400 a month at 4.0%. Running the balance forward, the target is reached after 3 years 3 months, around December 2029. By then you have paid in £18,600 in total, made up of the £3,000 you started with and £15,600 of monthly payments, and interest has added £1,446.
Now reverse the question. Suppose the money is needed in exactly three years instead. The starting £3,000 grows on its own over that time, and the rest has to come from payments, so the monthly figure needed is about £435. That is £35 more a month than the plan above, which is the price of pulling the date forward from 3 years 3 months.
What things move the answer?
- The monthly amount does most of the work on short goals. Under about five years, the balance is small for most of the period, so there is little for interest to act on. Raising the payment moves the date far more than chasing a better rate.
- Tax can reduce the interest. Interest above the Personal Savings Allowance is taxed at your normal rate, which the figures here do not deduct. Interest inside a cash ISA is never taxed and never counts towards the allowance.
- Rates are not fixed for years. Easy access rates move with the base rate and bonus rates often lapse after twelve months, so treat a single rate over a long goal as an illustration.
- Inflation is not deducted. If the target is an item you will buy, like a car or a deposit, its price may well rise while you save. Reviewing the target once a year is more useful than picking one number and forgetting it.
Common questions
How long will it take to save £20,000?
Starting from £3,000 and adding £400 a month at 4.0%, it takes about 3 years 3 months, arriving around December 2029. Of the £20,046 in the account at that point, £18,600 is your own money and £1,446 is interest. On shorter goals like this the interest is a useful top-up rather than the main contributor.
How much do I need to save each month to reach my goal?
Switch the calculator to the second option and give it a date. On the example figures, reaching £20,000 in three years from a £3,000 start at 4.0% needs about £435 a month. Pushing the same target out to five years drops the monthly figure sharply, because you get 60 payments instead of 36 and the interest has longer to work.
Does the interest rate matter much on a short savings goal?
Less than the monthly amount does. Over two or three years the balance spends most of its life well below the target, so there is not much money in the account for interest to act on. Over ten years or more the picture changes and the rate starts to carry real weight. For a short goal, focus on the monthly amount and on not drawing from the savings.
Should I use a cash ISA for my savings goal?
It depends on how much interest you will earn. Basic rate taxpayers can earn £1,000 of savings interest a year before tax is due, higher rate taxpayers £500, and additional rate taxpayers nothing. If your goal is small and short, an ordinary account paying a better rate can beat an ISA. If the balance is large, or you are a higher or additional rate taxpayer, the ISA wrapper is usually better because the interest stays tax free permanently.
How much should I keep in an emergency fund?
A common rule of thumb is three to six months of essential spending, held somewhere you can reach within a day or two. Work out your rent or mortgage, bills, food and travel for a month, then multiply. That figure makes a sensible first savings goal, ahead of longer targets like a deposit, because it is what stops an unexpected bill turning into debt.
Is it better to save a lump sum or monthly?
A lump sum earns interest from day one, so if you already have the money it will always outperform paying in the same amount gradually. Most people do not have the lump sum, which is why monthly saving is the normal route. The calculator handles both: put what you already have in the starting amount box and the regular payment in the monthly box.
What are the milestones along the way?
The milestones table breaks the target into a quarter, a half, three quarters and the full amount, and estimates when the balance reaches each one on the plan currently shown. Early milestones arrive mostly from the payments made in, while later ones include a growing share of interest. The dates use the monthly figure in the answer above, so changing that figure moves every milestone with it.
How is the savings goal figure worked out?
Each month the balance is multiplied by a growth factor derived from the entered interest rate, then the monthly payment is added. To find how long a goal takes, the calculation steps forward month by month until the balance reaches the target. To find the required monthly payment for a fixed date, the same relationship is rearranged so the target, the starting amount and the number of months give the payment needed.
What does a worked example look like?
On the default figures, a target of £20,000 with £3,000 already saved and £400 paid in monthly at 4.0% is estimated to be reached in about 3 years 3 months, around December 2029. Total contributions by then are estimated at £18,600, with interest adding a further £1,446. Pulling the deadline forward to three years instead raises the required monthly payment to about £435.
What things move the answer?
The monthly amount matters most on short goals, since the balance stays small for most of the period and there is little for interest to act on. Tax can reduce the interest actually kept, because amounts above the Personal Savings Allowance are taxed while a cash ISA is not. Savings rates are rarely fixed for years, and inflation is not deducted from any of the figures shown, so a rising price for the target item is not accounted for.
Sources & Rate Verification
Rates verified against official statutory guidance on 6 September 2026.