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UK Fin Lab
Professional-grade UK financial tools

HOMES

Rent Increase Calculator UK

Calculate the percentage change between your current and new rent, or project future rent using annual percentage or fixed-cash increases.

QUICK CHECK

Rent increase percentage calculator

Already know the old and new rent? Enter both amounts to calculate the percentage increase, monthly difference and extra annual cost.

Rent change +£35.00/month
Percentage change +5.00%
Annual difference +£420.00/year
New annual rent £8,820.00

FUTURE PROJECTION

Project future rent increases

Model repeated annual percentage increases or fixed cash increases over up to 40 years.

Starting annual rent £8,400.00
Projection period 10 years
Enter the annual percentage increase.
Optional modelling assumption. Examples: nearest £1, £5, £10 or £25.

Future rent projection

See the final modelled rent, total paid over the projection and the extra cost compared with keeping rent flat.

Final monthly charged rent £913.34
Total rent paid £96,296.59
Extra paid vs no increases £12,296.59
Final increase vs start 30.48%
Final raw rent before rounding £913.34
Projection period 10 years
Starting monthly rent £700.00

Year-by-year rent schedule

In percentage mode with rounding enabled, raw rent can keep rising in the background while charged rent only changes once it reaches the next rounding threshold.

Year Raw monthly rent Charged monthly rent Annual rent Annual increase Extra vs starting rent
Year 1 £700.00 £700.00 £8,400.00 £0.00 £0.00
Year 2 £721.00 £721.00 £8,652.00 £252.00 £252.00
Year 3 £742.63 £742.63 £8,911.56 £259.56 £511.56
Year 4 £764.91 £764.91 £9,178.91 £267.35 £778.91
Year 5 £787.86 £787.86 £9,454.27 £275.37 £1,054.27
Year 6 £811.49 £811.49 £9,737.90 £283.63 £1,337.90
Year 7 £835.84 £835.84 £10,030.04 £292.14 £1,630.04
Year 8 £860.91 £860.91 £10,330.94 £300.90 £1,930.94
Year 9 £886.74 £886.74 £10,640.87 £309.93 £2,240.87
Year 10 £913.34 £913.34 £10,960.09 £319.23 £2,560.09

Summary breakdown

Core assumptions and totals from the existing calculator logic.

Increase method Percentage (%)
Increase value 3.00%
Rounding used No
Round charged rent to —
Total with increases £96,296.59
Total with no increases £84,000.00
Extra paid vs flat rent £12,296.59

How to read this calculator

Year 1 is the starting-rent year. The first modelled annual increase is applied from Year 2.
For percentage increases, the calculator compounds the chosen percentage on the prior raw rent each year.
No rent rounding is applied to the charged rent.
If a tenancy or lease uses CPI, RPI or another index, enter the percentage required by the relevant clause. This tool does not fetch index data or interpret contract wording.
Use the output as a planning estimate rather than a legal or contractual rent review notice.

HOW TO USE IT

How to calculate a rent increase

If you know the current monthly rent and the proposed new monthly rent, the quick calculator above works out the cash increase, percentage increase and extra annual cost. For example, a rise from £800 to £840 is a £40 monthly increase, which is 5%, or £480 more over a full year.

If you instead want to model repeated annual rent rises, use the projection calculator. It can compound a percentage increase each year or add a fixed cash amount to the monthly rent.

Rent increase percentage formula

The percentage change is calculated from the difference between the new rent and old rent, divided by the old rent, then multiplied by 100. This is useful when a landlord has quoted a new rent but not the percentage increase.

Rent increase % = ((new rent − old rent) ÷ old rent) × 100

Using CPI or RPI for a rent increase

Some tenancy agreements, commercial leases or older leasehold agreements refer to an inflation index such as CPI or RPI. If your agreement tells you which percentage to apply, you can enter that percentage into the projection calculator above to model the arithmetic effect.

UK Fin Lab does not automatically fetch CPI or RPI data and does not decide which index, reference month, margin, cap, floor or review date applies to a contract. Those details depend on the wording of the relevant tenancy or lease.

Can this calculate a fair or legal rent increase?

No. A mathematical percentage increase is not the same thing as deciding whether a rent increase is legally valid or fair. Rules differ across England, Wales, Scotland and Northern Ireland, and may also differ for regulated tenancies, social housing, commercial leases and ground rent.

The calculator is designed for budgeting and comparison. Check the applicable tenancy or lease and current official guidance before relying on a proposed increase.

OFFICIAL GUIDANCE

Rent increase rules vary across the UK

Use the calculator for the numbers, then check the rules that apply where the property is located.

England GOV.UK private renting and rent increase guidance Wales GOV.WALES Renting Homes guidance Scotland Scottish Government rent and charges guidance Northern Ireland nidirect private rent and tenancy guidance

NEXT STEPS

Plan around a higher rent

Once you know the size of a rent increase, compare renting with buying, estimate mortgage costs or review the wider impact on your household budget.

Rent or buy

Rent vs Buy Calculator

Compare long-term renting and buying costs using rent, mortgage and growth assumptions.

 Buying costs

Mortgage Repayment Calculator

Estimate monthly mortgage payments, total interest and overall borrowing cost.

 Borrowing check

Mortgage Affordability Estimator

Estimate potential borrowing based on income, deposit and commitments.

 Income check

Take Home Pay Calculator

Estimate monthly net pay and compare a higher rent with take-home income.

Rent Increase Calculator FAQs

Subtract the old rent from the new rent, divide the difference by the old rent, then multiply by 100. The quick calculator above does this automatically and also shows the monthly and annual cash difference.

Enter your current and proposed new rent for a one-off increase, or use the projection calculator to model repeated annual percentage or fixed-cash rises.

Yes for the arithmetic: enter the percentage that your agreement requires. The calculator does not fetch the index, choose a reference month, interpret the clause or apply any contractual cap, floor or margin automatically.

You can use the percentage and projection maths as an illustration, but commercial rent reviews and ground-rent clauses can work in different ways. Check the exact lease wording before relying on the result.

No. It calculates the financial effect only. Tenancy type, location, notice requirements, market-rent rules and contract terms can all affect whether an increase is valid.

Most users simply want the mathematical percentage or cash increase. Rounding is an optional advanced assumption for agreements or modelling scenarios where the charged rent is rounded to a chosen increment.

Year 1 is shown at the starting rent. From Year 2 onward, the chosen percentage compounds on the previous raw rent or the chosen fixed cash amount is added each year.