Student loan overpayment calculator
Will overpaying your student loan pay off?
Put in your loan, salary and the extra you're weighing up. Across 10,000 possible futures, see how often paying extra actually saved money - and how often it went to a balance that was going to be cancelled anyway.
Free · No sign-up · Runs in your browser
Your loan
Pre-filled with a worked example - change anything and run again. Figures update only when you run the simulation.
Simulated outcomes
Paying extra does not always save money: in futures where the loan is written off first, the extra payments changed nothing. Here is how often each outcome happened for these inputs.
Updated for the 2026/27 tax year.
Running the worked example…
How this works
This tool plays out thousands of possible futures. In each one, inflation and your salary follow their own random path around a long-run average. Some futures are kind, some are not.
Student loan interest follows a measure of inflation called RPI (the Retail Prices Index). From February 2030, RPI is due to change so that it matches a lower measure called CPIH. Because of that, the simulated long-run inflation average steps down from 2030.
In every future, your plan's rules are applied one year at a time. Interest is added. Compulsory repayments are taken from income above the threshold. Any extra payments reduce the balance. This carries on until the loan is repaid, or written off (cancelled by law at the end of its term).
Each future is run twice: once with your extra payments and once without. The difference between the two runs is exactly what your extra payments changed. In futures where the loan was going to be written off anyway, they changed little or nothing - that money was lost.
Salary sacrifice (pay you give up before tax, for example for a pension or an EV lease) is taken off your income before repayments and Plan 2 interest are worked out. That covers both the percentage and the fixed monthly amount. A fixed monthly amount stays the same in cash terms unless the option to raise it with inflation is switched on.
The 'one steady example' table below the charts is a single scenario with all randomness switched off, so its rows always add up. It is not built from the chart bands - those describe different futures in different years, so they do not add up.
The 'what overpaying changed' figure adds up everything paid towards the loan - compulsory repayments and overpayments alike - in today's money, then compares the total with and without your overpayment at the middle (median) simulated future; a negative figure means overpaying cost more than it saved, because the balance was heading for write-off anyway.
The Plan 2 threshold comparison runs the same futures twice - once with the threshold freeze, once assuming the thresholds had kept rising with inflation (RPI). The gap between the two runs comes from the freeze alone; every other figure on the page includes the freeze.
Assumptions used by the model
This list comes straight from the model's own parameter file, so it always matches what the simulation really does.
Economy
- Inflation (RPI)
- starts at 4.1% and drifts back towards 3% a year until 2030, then towards 2.5% once RPI is aligned with CPIH (technical calibration: reversion speed 0.35, shock volatility 1.5%, floor -2%)
- Bank of England base rate
- held flat at 3.8% (only used for the Plan 1 and Plan 4 interest cap)
- Salary
- grows with simulated inflation plus 2% a year on top by default, with 3% year-to-year randomness (both adjustable under advanced assumptions)
- Time steps
- one year at a time, from today (2026/27 parameter year) to each plan's write-off date (set by law)
Plan 1
- Repayment
- 9% of income above £26,900 (2026/27)
- How the threshold moves
- rises each April with simulated RPI
- Interest
- lower of RPI and Bank of England base rate + 1%
- Write-off
- 25 years after the first April repayments were due
Interest is the lower of RPI and the Bank of England base rate plus 1 percentage point. Balances are written off 25 years after the first April repayments were due (loans from September 2006; older loans are cancelled at age 65, which this model does not cover).
Plan 2
- Repayment
- 9% of income above £29,385 (2026/27)
- How the threshold moves
- frozen until April 2030, then rises with simulated RPI
- Interest
- RPI up to RPI + 3%, rising with income between £29,385 and £52,885, capped at 6% for the one year from April 2026 only (the announced 2026/27 cap), with the normal rule resuming afterwards
- Write-off
- 30 years after the first April repayments were due
While repaying, interest tapers from RPI (income at or below the lower threshold) to RPI plus 3 percentage points (income at or above the upper threshold). A 6% cap applies for one year only, as announced for academic year 2026/27 (this model applies it to the 2026/27 tax year, from April 2026); the normal rule resumes afterwards, and any renewal of the cap - none is announced - would only lower the interest charged. The lower threshold is held frozen until April 2030 in this model. During study interest is RPI plus 3% throughout, which this model does not simulate - it assumes repayments have started or start from the year given. Written off 30 years after the first April repayments were due.
Plan 4 (Scotland)
- Repayment
- 9% of income above £33,795 (2026/27)
- How the threshold moves
- rises each April with simulated RPI
- Interest
- lower of RPI and Bank of England base rate + 1%
- Write-off
- 30 years after the first April repayments were due
Scottish loans. Interest is the lower of RPI and the Bank of England base rate plus 1 percentage point. Written off 30 years after the first April repayments were due (loans from 2007/08; older loans are cancelled at age 65, which this model does not cover).
Plan 5
- Repayment
- 9% of income above £25,000 (2026/27)
- How the threshold moves
- frozen until April 2027, then rises with simulated RPI
- Interest
- RPI only
- Write-off
- 40 years after the first April repayments were due
English loans for courses starting on or after 1 August 2023; the first repayments were due from April 2026. Interest is RPI with no income-linked addition. The threshold is frozen until April 2027 in this model, then rises with RPI. Written off 40 years after the first April repayments were due.
Postgraduate loan
- Repayment
- 6% of income above £21,000 (2026/27)
- How the threshold moves
- held flat for the whole simulation
- Interest
- RPI + 3%, capped at 6% for the one year from April 2026 only (the announced 2026/27 cap), with the normal rule resuming afterwards
- Write-off
- 30 years after the first April repayments were due
Postgraduate master's/doctoral loans (England and Wales). Repayments are 6% of income above the threshold and can run alongside an undergraduate plan's 9% - this version models ONE loan at a time, so postgraduate results ignore any concurrent undergraduate deduction. Interest is RPI plus 3 percentage points; a 6% cap applies for one year only, as announced for academic year 2026/27 (this model applies it to the 2026/27 tax year, from April 2026), and the normal rule resumes afterwards. Written off 30 years after the first April repayments were due.
How UK student loan repayments work
UK student loans do not behave like normal debts. What you pay each month depends only on what you earn, not on what you owe. And after a set number of years, whatever is left is cancelled.
Repayments follow your income, not your balance
You repay a fixed share of income above your plan's threshold: 9% for undergraduate plans, 6% for postgraduate loans. Earn below the threshold and you pay nothing at all that month.
Repayments usually come out of pay automatically, like tax. If your income falls, the payments fall too; below the threshold they stop. The size of the balance changes none of this - it only affects how long the payments might carry on.
Write-off: every loan has an end date
After a set term, the law cancels whatever balance is left - however large it is. That makes a UK student loan less like a mortgage and more like a time-limited extra tax. The clock starts from the first April after you were due to start repaying. The current terms by plan:
- Plan 1: 25 years
- Plan 2: 30 years
- Plan 4 (Scotland): 30 years
- Plan 5: 40 years
- Postgraduate loan: 30 years
Some older loans are cancelled at age 65 instead - GOV.UK has the exact rules for each start year. Write-off is why the simulations matter: money paid towards a balance that would have been cancelled anyway changed nothing.
Paying extra: the trade-offs
Extra payments shrink the balance today, which cuts the interest added later. In futures where the loan gets repaid in full, that brings the end date forward and lowers the total amount paid.
In futures where the loan reaches write-off, extra payments change nothing about the monthly amounts or the end date - the money is simply gone. Voluntary payments are normally not refundable.
Money sent to the loan cannot then do anything else. Points people commonly weigh up include interest on savings, employer pension matching, more expensive debts such as credit cards, and how likely their own salary is to carry them past full repayment. This page presents the simulated outcomes; the weighing up is yours.
Frequently asked questions
Will paying extra off my student loan always save money?
No. In simulated futures where the loan is written off before it is repaid, extra payments change nothing and that money is lost. How often paying extra helped depends on your plan, balance, salary and how many years are left.
What does write-off mean?
The law cancels whatever balance is left at the end of your plan's term - 25 to 40 years depending on the plan, counted from the first April after you were due to start repaying. Once written off, there is nothing more to pay.
Do UK student loans affect my credit score?
They do not appear on your credit file. A mortgage lender may still count the payslip deduction when working out what you can afford to borrow.
Which repayment plan am I on?
It depends on where you studied and when your course started. GOV.UK's guide to repaying your student loan lists every plan by country and start date.
Why does this tool show thousands of futures instead of one answer?
Because nobody knows future inflation or future salaries. A single answer would hide that uncertainty. Showing every simulated future lets you see how often each outcome happened, not just one guess.
Can I get voluntary payments back if I change my mind?
Normally no. Voluntary payments to the Student Loans Company are not usually refundable, which is one of the trade-offs of paying extra.
Does salary sacrifice change my student loan repayments?
Yes. Pay given up through salary sacrifice is not counted when repayments are worked out, so sacrificing pay lowers them. This tool can include both a percentage and a fixed monthly amount.
Is this calculator free, and where does my data go?
It is free and runs entirely in your browser. Nothing you type is sent or stored anywhere - there are no accounts and no cookies. Visits are counted in aggregate by Cloudflare Web Analytics, which is cookie-free and never sees what you type.
Guides and further reading
Plain explanations of how the rules actually work.
- Guide: how Plan 2 student loan interest actually worksWhere the Plan 2 rate comes from, how it rises with income, the one-year 6% cap for 2026/27 - and why the rate is not the whole story.
- Guide: when is my student loan written off?Write-off terms for every plan, when the clock starts, the age rules for older loans, and what cancellation means in practice.
- Analysis: the Plan 2 threshold freeze - who pays more, who pays lessThe same 10,000 futures simulated with and without the freeze: the lifetime difference by salary and balance, and the line where it flips to a saving.
- GOV.UK - Repaying your student loanThe official rules: which plan you are on, current thresholds and interest rates, and how repayments are collected.
- MoneyHelper - Repaying student loansFree, government-backed money guidance, including how student loan repayments work alongside the rest of your finances.
- MoneySavingExpert - Student loans mythbustingA widely read plain-English explainer of how the UK's earnings-based student loans really behave.
- Institute for Fiscal Studies - Student finance researchIndependent research on higher-education finance and what graduates actually end up repaying.