Rent Increase Calculator
Work out how much your rent will change using our calculator. Whether you’re dealing with index-linked reviews, percentage increases, or market rent adjustments, get instant, accurate results for residential and commercial properties across the UK.
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How to Use This Calculator
Calculating rent increases doesn’t have to be complicated. Here’s how to get the most out of each calculator mode:
Index-Linked Calculations
If your lease ties rent reviews to inflation indices like RPI, CPI, or CPIH, this is the mode for you. Simply enter your current rent, select which index your lease specifies, input the current rate (we’ve provided the latest figures), and specify how many years until review. The calculator will compound the increase if you’re looking ahead multiple years.
Percentage Increase Method
Got a fixed percentage increase written into your agreement? Or perhaps you’re a landlord considering what increase to apply? Enter your current rent and the percentage you want to calculate. This gives you an immediate figure for the new rent amount and shows exactly how much extra you’ll be paying or receiving annually and monthly.
Social Housing Rates
Social housing has specific government-mandated caps on rent increases. These are typically set at CPI plus 1%, though the exact rate varies year to year. We’ve pre-loaded the official rates for recent years so you can quickly see what your new rent should be.
Custom Index Values
Commercial leases often reference specific index values from particular months. If your lease states something like “the rent shall be adjusted based on the ratio of the Index for Month X to the Index for Month Y,” this calculator handles that. Just input both index values and your current rent.
What You Need to Know About Rent Increases
Residential Rent Reviews
For private residential tenancies in England, landlords can’t just increase rent whenever they fancy. They must wait at least 12 months from the start of the tenancy or the last increase. From May 2026, new rules require landlords to give two months’ notice (up from one month previously) and increases are limited to once per year.
Commercial Property Reviews
Commercial leases work differently. Most include rent review clauses that activate at predetermined intervals, typically every three or five years. These reviews usually fall into one of three categories: market rent revaluations, index-linked adjustments (using RPI, CPI, or CPIH), or turnover-based calculations for retail premises.
Index-linked reviews became popular because they’re straightforward and avoid disputes over comparable evidence. However, there’s a significant change coming: by February 2030, RPI will be reformed to align with CPIH, which will affect all leases still referencing RPI.
The Three Main Inflation Indices
RPI (Retail Price Index) has been around since 1947 and measures changes in the cost of retail goods and services. It’s traditionally been higher than CPI, which is why landlords prefer it. CPI (Consumer Price Index) is now the UK’s primary inflation measure and tends to produce lower figures. CPIH extends CPI by including housing costs and council tax, making it the most comprehensive measure.
| Index | Current Rate | Best For | Notes |
|---|---|---|---|
| RPI | 4.3% | Older commercial leases | Being phased out by 2030 |
| CPI | 3.6% | Modern agreements | Official UK inflation measure |
| CPIH | 3.8% | Comprehensive reviews | Includes housing costs |
Timing Matters
Index figures are published monthly by the Office for National Statistics, typically around the 17th of each month for the previous month. Well-drafted leases specify that the base index month and review index month should be two months before the relevant dates. This ensures the figures are available when needed. If your lease specifies one month before, you might have to wait for publication, which could delay the review process.
Worked Examples
Example 1: Index-Linked Commercial Review
Sarah runs a café with a five-year lease that started in 2020 with annual rent of £18,000. Her lease specifies rent reviews every five years using RPI. The base RPI was 100.0, and the current RPI is 121.5.
Calculation: (121.5 ÷ 100.0) × £18,000 = £21,870
Result: Sarah’s new annual rent is £21,870, an increase of £3,870 per year (£322.50 per month).
Example 2: Annual Percentage Increase
Mark rents a flat for £14,400 per year. His landlord has served a Section 13 notice proposing a 4.5% increase.
Calculation: £14,400 × 1.045 = £15,048
Result: The new annual rent would be £15,048 (£1,254 per month), an increase of £648 annually or £54 monthly.
Example 3: Social Housing Cap
Jennifer lives in social housing paying £7,800 per year. For 2025-26, the increase is capped at 2.7%.
Calculation: £7,800 × 1.027 = £8,010.60
Result: Jennifer’s rent increases to £8,010.60 annually (£667.55 monthly), a rise of £210.60 for the year.
Example 4: Multi-Year Projection
A landlord wants to project rent over three years with annual 3.5% increases, starting from £16,000.
Year 1: £16,000 × 1.035 = £16,560
Year 2: £16,560 × 1.035 = £17,139.60
Year 3: £17,139.60 × 1.035 = £17,739.49
Result: After three years, the rent reaches £17,739.49, a total increase of £1,739.49.
Common Questions Answered
For private residential tenancies, legally there’s no cap, but increases must reflect market rates. If you believe an increase is excessive, you can challenge it through the First-tier Tribunal. They’ll assess whether the proposed rent aligns with similar properties in your area. Social housing has strict caps set by government policy.
For most residential tenancies, once per year is the maximum. Commercial leases specify review intervals in the agreement, commonly every 3-5 years. The new Renters’ Rights Act maintains the annual limit but extends notice periods from one to two months starting May 2026.
This creates ambiguity and potential disputes. If your lease simply says “in line with inflation” without specifying RPI, CPI, or CPIH, you may need legal advice. Generally, courts interpret such clauses, but it’s far better to have clarity upfront. For new agreements, always specify which index applies.
Residential tenants can challenge increases they believe exceed market rates via the First-tier Tribunal. However, landlords can serve notice to end the tenancy if you refuse a reasonable increase (though from May 2026, rules change significantly). Commercial tenants are bound by their lease terms unless they can prove the calculation is incorrect.
Leases currently using RPI will need addressing. Some may automatically transition to CPIH, others might require renegotiation. This particularly affects long commercial leases. If you have an RPI-linked lease extending beyond 2030, consider seeking professional advice on how the transition will work.
Index-linked reviews can theoretically result in decreases if the index falls, though this is rare. During the 2010-11 period, for instance, some indices went negative. Most commercial leases include “upward only” clauses preventing decreases. Residential landlords voluntarily reduce rent in some cases to retain good tenants, but there’s no obligation.
The Office for National Statistics publishes all index figures monthly on their website. You need the specific month and year referenced in your lease. For commercial reviews, your lease should specify exactly which months to use for base and review calculations. Keep records of these figures as they’re essential for verification.
This varies by location and property type. Currently, with inflation indices around 3-4%, many landlords apply similar increases. In high-demand areas, market-driven increases can be higher. Social housing is capped at CPI + 1%. Always compare proposed increases against both inflation rates and local market conditions.
Making Sense of Your Lease Terms
Key Clauses to Look For
Your lease or tenancy agreement should clearly state when and how rent can increase. For index-linked reviews, look for the specific index mentioned (RPI, CPI, or CPIH), the base date or base index value, the review frequency, and which months’ indices will be used. Commercial leases often include collar and cap provisions limiting how much rent can decrease or increase at each review.
The Base Index Concept
Many commercial leases establish a base index value at the start of the lease, often set at 100.0 for simplicity. At each review, the current index value is compared to this base. So if the base is 100.0 and the review index is 125.0, your rent increases by 25%. Some leases use actual index values from specific dates rather than rebasing to 100.
Compounding vs Simple Increases
Most index-linked leases compound increases. This means each review uses the previous rent as the starting point. If your initial rent is £10,000 and it increases by 10% to £11,000, the next review applies the percentage to £11,000, not the original £10,000. Over long periods, compounding significantly affects total rent paid.
Recent Changes and What’s Coming
The Renters’ Rights Act 2025
Royal Assent was granted in October 2025, with major reforms taking effect from 1 May 2026. Key changes include extending the notice period for rent increases from one to two months, maintaining the limit of one increase per year, and strengthening tenants’ rights to challenge excessive increases. Landlords will need market evidence to support proposed increases.
Social Housing Rent Policy
For 2025-26, social housing rent increases are capped at 2.7% (CPI + 1%). This is substantially lower than the 7.7% cap from 2024-25. The government sets these limits annually based on September’s CPI figure. Specific exemptions apply to supported housing, domestic violence refuges, and certain other categories.
The RPI Transition
By February 2030, RPI will be reformed to align with CPIH methodology. This affects thousands of commercial leases. CPIH tends to produce slightly higher figures than CPI but lower than traditional RPI. Landlords and tenants with long leases should review their agreements now to determine how this transition will be handled.
Tips for Landlords and Tenants
For Landlords
Always provide proper notice using the correct procedure. For residential properties, this means a Section 13 notice with appropriate timing. Keep market evidence supporting your proposed increase in case of challenge. Consider the long-term relationship with good tenants – sometimes a modest increase that keeps a reliable tenant is better than maximising rent and facing void periods.
For commercial properties, mark review dates well in advance. Missing a review date can mean waiting until the next scheduled review, potentially losing years of increased income. When using index-linked reviews, verify you’re using the correct months as specified in the lease.
For Tenants
Know your rights and the specific terms of your agreement. If you receive a rent increase notice, check it’s procedurally correct and the amount is reasonable. Research comparable properties in your area – websites like Rightmove and Zoopla show market rates. If challenging an increase, gather evidence of similar properties renting for less.
For commercial tenants, review your lease well before each review date. Consider whether market rent might actually be lower than an index-linked increase would produce. Some leases allow you to request market rent reviews instead of automatic index increases.