What this calculator assumes, and where it stops
You're thirtyish and you'd like to know how much to trust a number on the internet.
Every figure comes from one calculation that gets tested
81 automated tests, run before anything reaches this site.
There is a single calculation engine behind every page here. It is checked against the repayment regulations rather than against other calculators, it has no connection to a spreadsheet anyone typed by hand, and the same code produces the worked examples in the explanations as produces your answer.
That doesn't make it right. It makes it consistent, and it means a mistake is one mistake rather than nine.
Three assumptions do most of the work
Change these and the answer moves more than anything else you can type.
| Assumption | Default | What it affects |
|---|---|---|
| Inflation (RPI) | 3% a year | Interest, and how thresholds rise |
| Bank Rate | 4% | Interest on Plans 1 and 4 only |
| Earnings growth | A real premium that varies with age | Everything |
Both of the first two are editable. Neither is a forecast — nobody can forecast thirty years of inflation, including the people who publish the official ones.
Your age changes the answer by a factor of three
Same balance, same salary, same plan: totals from £38,511 to £12,436.
Earnings don't rise at a steady percentage through life. They rise fastest in your twenties and flatten in your forties, so when you are on that curve decides almost everything about whether you clear the loan. That's why the tool asks your year of birth and won't let you skip it.
The earnings path, and the assumption inside it that may not fit you
Real earnings growth above inflation, from the government's own graduate outcomes data and the ONS earnings survey:
Age Real growth a year 22–26 +7.94% 26–31 +2.66% 31–34.5 +2.58% 34.5–44.5 +0.85% 44.5+ −0.55% ⚠️ It assumes you graduated at 21. The underlying data is published by years since graduation, so the tool converts your age using that assumption. A mature student, a four-year course, a year out or a career change all shift the whole curve against your real position — and the direction is usually against you, because it puts you further along a flattening curve than you actually are.
This is the weakest assumption in the tool and it is not hidden in the code.
Four places where the law is less settled than the number looks
Real numbers, genuinely uncertain foundations.
The one worth knowing about is Plan 4. Schedule 1A hands Scottish thresholds to the Scottish regulations, and I haven't read them — so the tool uprates Plan 4 by analogy with the other plans. If you applied through SAAS, treat your figure as the least certain on this site. The other three are below.
All four, in the order they'd cost you
The Plan 2 threshold freeze is announced, not law. The freeze from April 2027 to April 2030 was announced at the Autumn Budget 2025 and the regulations still carry the old uprating rule. The tool applies the freeze because it is real policy, and shows what it costs you separately — but a statutory instrument has to arrive for it to be more than an announcement.
Plan 4's threshold uprating is assumed, not verified. Schedule 1A defers Plan 4 to the Scottish regulations, and I have not read them. It is uprated here by analogy with Plans 1, 2 and 5. If you are a Scottish borrower, treat your figure as less certain than the others.
The 6% interest cap is a one-year policy, not a permanent feature. It is reviewed, and it can move.
The Postgraduate threshold has no uprating mechanism at all. The regulation says "£21,000" and stops. It has not moved since 2016, and nothing in law says it ever will.
Four things it deliberately doesn't do
Named, rather than left for you to discover.
It doesn't model overpayments — that page explains what one actually does. It doesn't model the age-65 write-off that applies to loans first paid before 2006. It doesn't replay years you've already repaid, because their effect is already inside the balance you typed in. And it cannot know what you will actually earn, which is the assumption every other one rests on.
One rounding rule I know about and haven't implemented
The regulations round each uprated threshold up to the nearest £5. The engine doesn't. The gap is at most £5 of threshold, which is about £0.45 a year of repayment — recorded here because "we know and it's small" is a different statement from "we didn't notice".
Why I'd rather show you all of this
A calculator that hides its assumptions is asking you to trust it twice.
Every tool on this subject makes these choices. Most don't tell you which ones they made, which means you can't tell a careful answer from a confident one.
I can't tell you what to do about your own loan. This is information rather than advice.
2026/27 tax year. Engine tested against the Education (Student Loans) (Repayment) Regulations 2009, consolidated to 1 April 2026.