Rent review calculator: CPI and RPI
Work out an index-linked rent review from the official inflation figures, with a collar, a cap and the upward-only rule if your lease has them.
The minimum rise, e.g. 1
The maximum rise, e.g. 4
The reviewed rent
Enter the rent to see the reviewed figure.
How an index-linked review works
The lease names an index (usually CPI or RPI) and two index months. The new rent is the old rent multiplied by the later index figure and divided by the earlier one. Many leases add a collar (a minimum rise) and a cap (a maximum), often a percentage a year compounded over the review period; some cap the total instead. Most are upward-only, so the rent can't fall at a review.
Worked example
A rent of £40,000 a year, reviewed five years on, from August 2021 to August 2026:
| Basis | Index change | New rent |
|---|---|---|
| CPI, no cap or collar | 28.1% | £51,239.96 |
| CPI, collar 1% and cap 4% a year, compounded | 28.1% | £48,666.12 (capped) |
| RPI, no cap or collar | 37.2% | £54,860.12 |
CPI or RPI?
Use the index your lease names. RPI has usually risen faster than CPI, so the choice matters, and the ONS no longer treats RPI as a national statistic. If the lease's index stops being published, the lease should say what replaces it.
Before you agree a review clause
The index, the months, how the cap and collar compound and what happens if the index changes are all in the lease's wording. Tell us about the lease and we'll introduce you to an independent SRA-regulated solicitor we work with.
Sources
- ONS: CPI index, all items (series D7BT, 2015=100)
- ONS: RPI all items index (series CHAW, January 1987=100)
Index figures to August 2026, published by the ONS on 16 September 2026. A calculation, not advice: your lease decides how the review works.