Planner
Work backwards from what you can spare
Tell us what's realistic each month and we'll rank the ways to use it — then solve for the date you want to be free.
£300
To hit 2045
About £500 extra a month.
Found by running your full schedule repeatedly and narrowing in — the same maths as the table, not a shortcut.
Ranked · what £300 a month can do
Step up the monthly payment 10% a year
No lump sums — the monthly payment itself grows
Saved
£78.8 K
Time
13y 4m
Extra paid
£142.9 K
Monthly top-up
with every monthly payment
Saved
£50.8 K
Time
6y 11m
Extra paid
£64.8 K
Quarterly top-up
every three months
Saved
£50.4 K
Time
6y 11m
Extra paid
£64.8 K
Yearly lump sum
saved up, paid once a year
Saved
£48.7 K
Time
6y 10m
Extra paid
£64.8 K
Ranked by interest saved for the same outlay. Paying earlier always beats paying later — that's where the interest lives.
Payoff planner
Build your plan on the left. Watch it pay off on the right.
No Calculate button — every number updates as you type, and each figure traces back to a row in your schedule.
Your loan
What you owe today
Your overpayments
Lump sums or top-ups
Choose the outcome
Shorter loan or lower monthly payment
Results, live
No Calculate button
Your loan
What you owe today
Computed from the numbers above.
Your overpayment plan
1 active · £47.4 K overpaid over the loan
from 05 Nov 26
On its own: saves £37.6 K and 5y 1m off your loan.
What should overpaying do?
The single most important choice here
Advanced optionsPayment frequency, rate changes, fees — optional
Payment mechanics
Interest rate changes
Your monthly payment is recomputed over the term remaining, so the end date does not move. Your lender's letter says which it does.
Fees & charges
Only if your deal has one — see your mortgage offer for the rate and allowance.
Of the balance at the start of each calendar year — check your offer.
Net benefit after fees
£37.6 K
No fees entered, so the whole saving is yours.
Where you stand after
Side by side
Your loan with your plan, and without it
Two futures for the same loan. The right-hand column is the one you're building.
Interest you keep
£37.6 K
23% less interest than doing nothing
Time you get back
5y 1m
earlier than Sep 2051
Every figure here is the last row of the matching schedule below — nothing is estimated separately.
Visual proof
Your balance reaches zero 5y 1m sooner
The shaded gap is what you no longer owe. At its widest it is £75.7 K.
Where each year's instalments go
Interest outweighs principal until 2034 — which is why an overpayment made before then removes the most.
What waiting costs you
What £30.0 K removes from your interest bill, by the date you pay it.
Paid now it removes £51.4 K. Wait twelve months and it removes £48.2 K — £3.2 K less for the same money.
Full detail
Every payment, to the penny
239 payments across 21 years, every penny accounted for
21 years match
| # | Date | Opening | Payment | Interest | Principal | Overpayment | Closing |
|---|---|---|---|---|---|---|---|
| £250,000 | £4,548 | £2,775 | £1,772 | £400 | £248,228 | ||
| £248,228 | £18,990 | £10,882 | £8,108 | £2,400 | £240,120 | ||
| £240,120 | £18,990 | £10,514 | £8,476 | £2,400 | £231,644 | ||
| £231,644 | £18,990 | £10,129 | £8,861 | £2,400 | £222,783 | ||
| £222,783 | £18,990 | £9,726 | £9,264 | £2,400 | £213,519 | ||
| £213,519 | £18,990 | £9,306 | £9,684 | £2,400 | £203,835 | ||
| £203,835 | £18,990 | £8,866 | £10,124 | £2,400 | £193,711 | ||
| £193,711 | £18,990 | £8,406 | £10,584 | £2,400 | £183,127 | ||
| £183,127 | £18,990 | £7,925 | £11,065 | £2,400 | £172,062 | ||
| £172,062 | £18,990 | £7,423 | £11,567 | £2,400 | £160,495 | ||
| £160,495 | £18,990 | £6,897 | £12,093 | £2,400 | £148,402 | ||
| £148,402 | £18,990 | £6,348 | £12,642 | £2,400 | £135,760 | ||
| £135,760 | £18,990 | £5,774 | £13,216 | £2,400 | £122,544 | ||
| £122,544 | £18,990 | £5,174 | £13,816 | £2,400 | £108,728 | ||
| £108,728 | £18,990 | £4,546 | £14,444 | £2,400 | £94,284 | ||
| £94,284 | £18,990 | £3,890 | £15,100 | £2,400 | £79,184 | ||
| £79,184 | £18,990 | £3,204 | £15,786 | £2,400 | £63,398 | ||
| £63,398 | £18,990 | £2,487 | £16,503 | £2,400 | £46,896 | ||
| £46,896 | £18,990 | £1,738 | £17,252 | £2,400 | £29,643 | ||
| £29,643 | £18,990 | £954 | £18,036 | £2,400 | £11,608 | ||
| £11,608 | £11,791 | £183 | £11,608 | £1,400 | £0 | ||
How we calculate
No black box. Six rules produce every number here.
The same six a lender applies to your account each month. Read them, check them against your statement, then trust the schedule.
Interest accrues on your opening balance each period. On the default settings — monthly payments, monthly compounding — that is your annual rate divided by twelve, which is standard reducing balance. Change the payment frequency and the rate is converted so your effective annual rate stays the same.
An overpayment goes entirely to principal. Nothing is applied to interest, which is why the next period costs you less.
No period ever pays more than the balance plus its interest, so the loan settles at exactly zero and can never go negative.
On a rate change the monthly payment is recomputed over the term remaining — term held, monthly payment moves.
Both futures are run through the same engine on the same rate path, so the comparison is fair.
Every headline figure is the last row of its schedule. Nothing on this page is estimated a second way.
Questions people ask
What if my target date is not achievable?
The planner will say so rather than returning a misleading figure. If clearing the balance by your target would require an overpayment beyond a plausible range, it reports the goal as unreachable. Move the target later, or use the ranking to see what the money you do have available actually buys.
Does this account for my early repayment charge?
Only if you enter it. Under Advanced options, add the charge, your penalty-free allowance and the date your deal ends. The charge is then applied only to each calendar year's overpayments above the allowance, and only until the deal ends — which is how lenders apply it — and subtracted from the net benefit. Most fixed and discounted deals allow around 10% a year without charge, so a modest monthly overpayment often attracts none.
Is it better to overpay monthly or save up for a yearly lump sum?
Monthly, if the only question is interest. Each overpayment starts reducing the balance from the next payment, so money paid in through the year works for longer than the same money held back and paid at the year end. The planner's ranking prices the gap on your own mortgage. It does not count interest the money might earn in savings while you wait, so set that against the gap yourself.
What should I enter as the outstanding balance?
What you still owe today, from your latest mortgage statement — not the amount you originally borrowed. This is the single most common mistake, and it changes every number on the page.
Will my lender charge me for overpaying?
Only if your deal has an early repayment charge, and usually only on the part above your allowance. During a fixed or discounted deal most lenders let you overpay a set amount each year without charge — commonly 10%, though some allow 20% — and the charge, often 1–5% and stepping down each year of the deal, applies to the amount above it. Lenders differ on the detail: some measure the allowance against your current balance and some against the original loan, and some reset it each calendar year and some on the deal's anniversary. On a standard variable rate, and on most trackers, there is usually no limit and no charge. Enter your deal's charge, allowance and end date under Advanced options and the net benefit updates. Checked against lenders' published terms on 10 September 2026.
Why does my lender's number differ slightly?
This calculator charges interest at your annual rate divided by twelve on the balance at the start of each month, and an overpayment takes effect from your next scheduled payment. Many lenders calculate interest daily and credit an overpayment on the day it arrives, so you will save a little more than shown — at most about one month of interest on the amount overpaid.
Where does my data go?
Nowhere. Every calculation runs in your browser. There is no account, no tracking of your mortgage details, and no server round-trip to compute any of this.
Why you can check this one
Independent
Not a lender, not a broker, not affiliated with anyone who is. Nothing here is ranked by what it pays us, because nothing pays us. There are no ads and no lead generation.
Checkable
Every figure is the last row of a schedule you can expand, read and download. The rules the engine follows — the rate conversion, the rounding points, how an overpayment is timed — are published in full, along with every place we knowingly differ from a lender.
Honest about limits
It models the loan, not your life. It does not know your lender's exact day-count conventions, your emergency fund or your tax position — and it will tell you when overpayment costs more than it saves rather than showing you a zero.
Nothing you type is sent anywhere. No account, no tracking of your loan details, nothing stored on a server. How that works.
Read the full methodology — the exact rate conversion, where rounding is applied, how we time an overpayment, and every choice we make differently from a lender, with the reasoning for each.
In plain terms
Planning backwards from a date instead of forwards from a payment
Most calculators ask what you will pay. This one also answers the more useful question: what would it take?
Working forwards — "if I overpay £200 a month, when am I clear?" — is the easy direction, and every calculator does it. Working backwards is the direction people actually think in: "I want to be mortgage-free by the time the children start university; what does that cost me each month?" There is no closed-form answer to that question, because the payoff date is not an invertible function of the overpayment. It has to be solved numerically.
The planner does exactly that. It runs your complete schedule repeatedly, adjusting the monthly overpayment and narrowing the interval until the payoff date lands on your target. It is the same engine and the same arithmetic as the schedule table below — not a simplified approximation used only for this panel — so the figure it returns will reconcile exactly with the schedule when you apply it.
It also answers the question in the other direction, which is often the more honest one. Tell it what you can genuinely spare each month and it ranks the ways to deploy that money: as a monthly overpayment, quarterly, saved up and paid annually as a lump sum, or as a steadily rising payment. Paying earlier beats paying later in every ranking it produces, because that is where the interest lives.
How it's calculated
The working behind the number
This mortgage payoff calculator works backwards. Give it the year you want to be mortgage-free and it finds the monthly overpayment that clears the balance by then, by re-running your full schedule and narrowing the amount until the payoff date lands on target. Give it what you can spare each month instead and it ranks the ways of paying that money in by the interest each one saves.
Formula
Balanceₖ = Balanceₖ₋₁ × (1 + r) − Monthly payment − X, solved for the smallest X that brings the balance to 0 by your target date
- Balanceₖ₋₁
- What you owe before payment k. The first is the outstanding balance you enter.
- r
- The monthly rate: your annual rate ÷ 12.
- Monthly payment
- Your contractual repayment, from P × r × (1 + r)ⁿ ÷ ((1 + r)ⁿ − 1), or the figure you type.
- X
- The monthly overpayment the planner solves for.
Assumptions and limits
- The overpayment is the same every month from your next payment, and your monthly payment stays the same, so the term shortens.
- The amount is found by re-running the full schedule up to 32 times and narrowing in, so it reconciles with the schedule table.
- Interest is charged monthly on the reducing balance at the annual rate ÷ 12, rounded to the penny each month; lenders that charge interest daily will differ slightly.
- An early repayment charge does not change the overpayment needed — it is paid out of pocket, never added to the balance — but is subtracted from the net benefit if you enter it.
A worked example
Take £250,000 outstanding at 4.45% a year, with 25 years (300 monthly payments) of term left, and a goal of being clear by the end of 2045.
- Monthly rate r = 4.45% ÷ 12 = 0.3708%.
- As it stands the term runs to Sep 2051.
- The planner searches the full schedule for the smallest monthly overpayment that clears it by the target.
£500 a month on top of the monthly payment clears it in Jan 2042, saving £69.8 K of interest.
Computed by the calculator on this page, from the figures it opens with.
Sources
- FCA Handbook, MCOB 12.3: an early repayment charge must be a reasonable pre-estimate of the lender's costs — checked 10 September 2026
- Bank of England, Effective interest rates, July 2026: 4.45% effective rate on new UK mortgages — the rate this page opens on — checked 10 September 2026
By The CutYears team · Last reviewed 10 September 2026 · Full methodology