2026-27 constants used
| Plan | Threshold | Rate | Interest | Write-off |
|---|---|---|---|---|
| Plan 1 | £26,900 | 9% | 3.2% | 25 years |
| Plan 2 | £29,385 | 9% | 3.2%–6.2% sliding | 30 years |
| Plan 4 | £33,795 | 9% | 3.2% | 30 years |
| Plan 5 | £25,000 | 9% | 3.2% | 40 years |
| Postgraduate | £21,000 | 6% | 6.2% | 30 years |
Current RPI: 3.2% (March 2025 figure, applies September 2025 to August 2026).
Formulas
Monthly repayment for a single plan: (gross_annual_salary − threshold) × rate ÷ 12. If salary is at or below the threshold, repayment is zero.
For multiple undergraduate plans, repayment is calculated against the plan with the lowest threshold (per gov.uk rules). The Postgraduate Loan is always calculated separately and stacks on top.
Interest is applied monthly using balance × (annual_rate ÷ 12). Plan 2 uses a sliding interest rate based on income, modeled as a linear interpolation between RPI at the lower threshold (£29,385) and RPI+3% at the upper threshold (£52,885).
Salary growth is applied annually by default at 3%. The user can adjust this between 0% and 5%. We don't model bonuses, irregular income, or career breaks; these would all reduce repayments below our estimate.
Loan write-off occurs at the end of the plan's write-off period (25 / 30 / 40 years from when the borrower became liable to repay). Any remaining balance is cancelled.
What's fixed and what changes
The repayment rate (9% for Plan 1/2/4/5, 6% for Postgraduate) is set in UK legislation and has not changed since 1998. It is not market-linked, not BoE-linked, not subject to government discretion at the margin. It applies uniformly to every borrower on that plan.
The interest rate changes quarterly — every March, June, September, and December — based on the latest RPI figure and (for Plan 1 and Plan 4) the Bank of England base rate. The current rates we display are correct as of September 2025. They may have changed by the next quarterly review.
The repayment threshold changes annually each April. We update the calculator constants every April when new figures are announced.
Update procedure
This site is updated:
- Annually, in late March / early April, when new tax-year thresholds and rates are announced
- Quarterly, when interest rates change at the start of March, June, September, December (light-touch update — we revise the displayed rates and the "as of" date)
If you spot an out-of-date figure, email us at hello@repaymyloan.co.uk. The site's accuracy is its only reason to exist.
Assumptions
- You're employed (PAYE), not self-employed.
- Your salary grows at a constant annual rate (you choose 0% to 5%).
- You don't take a career break, parental leave, or extended unemployment.
- You stay in the UK and don't trigger overseas-threshold rules.
- Interest rates and thresholds change broadly in line with current rules.
- The government doesn't make further changes to plan terms (a real risk over 30-40 year horizons).
These simplifications mean our estimates are best for understanding broad shape and decision-making, not for predicting your exact lifetime cost decades into the future.
Sources
- Student Loans Interest Rates and Repayment Threshold Announcement (gov.uk)
- Student loans: terms and conditions 2026 to 2027 (gov.uk)
- Repaying your student loan: how much you repay (gov.uk)
- Student loans interest rates and repayment thresholds FAQs (House of Commons Library)
Our calculator is independent and we tested it against the worked examples published at gov.uk to verify accuracy before launch. Every plan-specific page also documents the figures we used so you can check our work.