Self storage KPIs for UK operators: 12 numbers and what each divides by

Every number in this guide was read on 16 October 2026, and its main finding is that one KPI is printed on different divisors. At 31 October 2025 Safestore gave its UK occupancy as 75.6% of maximum lettable area and 79.9% of current lettable area, for the same stores on the same day. This guide sets out twelve KPIs, what each divides by and what UK operators publish.

Why does one KPI give several numbers?

A ratio needs a denominator, and operators choose different ones. Big Yellow divides occupied space by its maximum lettable area (MLA), the total square feet it can let. Safestore also prints occupancy of its current lettable area (CLA), which leaves out space not yet fitted out and space that is operationally unavailable.

At 31 October 2025 Safestore’s UK stores had 4.52 million sq ft occupied, 5.98 million of MLA and 5.66 million of CLA. That is 75.6% of MLA and 79.9% of CLA, a gap of 4.3 points from the denominator alone (our calculation). Its figures for 30 April 2026 show a gap of similar size: 72.5% against 76.7%.

The stores counted matter as well. Big Yellow’s closing occupancy at 31 March 2026 was 74.2% for all stores, 77.0% for like-for-like stores, which leave out stores acquired, opened or closed in the year, and 78.2% for its 77 “same stores”, those that have reached 85% occupancy in an earlier year.

Big Yellow wrote: “Overall store occupancy, with four new stores opening in the year, was 74.2% (2025: 78.7%).” Three labels travel with every KPI: what it divides by, which stores it counts and the date it was taken.

Which occupancy should you track?

There are three, and the UK sources we read define only one of them. Occupancy by units is the share of lettable units with a customer in them. Occupancy by area is the share of lettable floor area that is occupied. Economic occupancy is the licence income actually contracted, as a share of what every lettable unit would earn at list price. These are our definitions.

On 16 October 2026 we found no definition of economic occupancy, and no occupancy by units, in the documents we searched. We searched the results and trading updates of Big Yellow, Safestore, Shurgard and Lok’nStore, and the Self Storage Association UK’s (SSA) 2025 and 2026 reports. Every occupancy they publish is by area.

The published figures are therefore the ones to set your area occupancy beside. Big Yellow was at 74.2% of MLA at 31 March 2026. Safestore UK was at 79.9% of CLA at 31 October 2025. The SSA put all stores at 74.5% of CLA in 2025 and mature stores, those not opened or expanded in four years, at 79.6%. Shurgard’s UK same stores, its London stores, averaged 87.0% in 2025.

Each measure hides something the others show. A unit count treats a 10 sq ft locker like a 300 sq ft room, and a count by area lets a few big rooms outweigh many small ones. Economic occupancy shows what discounts are costing. Our reading: choose one definition of each, write it at the top of the report and do not change it in mid-year.

StoreBay’s Occupancy report shows how full each site and each unit type is right now: occupied units as a share of lettable units, with reserved units not yet counted as occupied. Its spreadsheet and PDF downloads add, for each site, occupancy by floor area and economic occupancy: the licence income actually contracted as a share of what every lettable unit would earn at list price.

What is a pound per square foot a pound per?

Three sources print an annual figure per occupied square foot. Big Yellow’s average for the year to 31 March 2026 was £35.98 (its results call it “net rent” per sq ft). Safestore UK’s average rate for the year to 31 October 2025 was £30.68. The SSA’s revenue per sq ft for 2025 was £27.40, excluding VAT. Big Yellow and Safestore also state their revenue without VAT.

Every figure per square foot in those documents is for a year, and on 16 October 2026 we found no figure per week. Dividing by 52 gives about £0.69 a week for Big Yellow, £0.59 for Safestore UK and £0.53 for the SSA (our calculation).

The SSA’s 2025 report titled its chart “return per square foot on occupied space ex VAT”. Its 2026 report says only revenue per sq ft, excluding VAT, and we read £27.40 as the same measure, which is our inference. That report prints the fall into 2025 as 5.1% in one place and 5.4% in another, and a regional section gives a 7.4% fall to £26.97.

Revenue per available square foot (REVPAF) divides revenue by space that could be let, occupied or not. Safestore divides revenue by its weighted average available sq ft: £29.24 for its UK stores in the year to 31 October 2025. Big Yellow divides total store revenue by its average MLA: £31.84 for the year to 31 March 2026.

The two are not the same sum. Big Yellow’s average rate times its average occupancy of 77.2% gives £27.78 per available sq ft (our calculation), below its REVPAF of £31.84, because REVPAF starts from total store revenue of £207.6 million while the rate starts from self storage income of £181.1 million. Safestore calls REVPAF “the net outcome of the occupancy/rate mix plus ancillary sales”.

Unit mix moves these figures too. Safestore says smaller units earn more per sq ft, which lifts its average rate. Big Yellow says its domestic customers occupy 59 sq ft on average and pay 16% more per sq ft than business customers, because their rooms are smaller. The portfolios differ in size, place and age, so the figures are not a ranking of operators.

What do churn and length of stay count?

The SSA defines churn as move-outs divided by the average number of occupied units over a year. It is a unit count, where its occupancy is by area. A churn of 100% means, in the SSA’s words, that “one customer leaves for every unit”, so an operator with 400 occupied units needs 400 new customers to hold occupancy.

SSA churn was 131% in 2015, 117.5% in 2019 and a record low of 76.5% in 2021. It was 97.5% in 2023, 97.1% in 2024 and 96.6% in 2025. The SSA’s 2025 report notes that a store usually lowers its churn as it ages, because it collects long-stay customers.

Length of stay is a different count. Safestore UK’s average length of stay for the year to 31 October 2025 was 17.3 months for domestic customers and 26.0 months for business customers; on 16 October 2026 we found no statement in its release of whether it counts customers who have left or those still there.

Big Yellow says some 60% of its customers vacate within six months. Its results presentation also gives the average length of stay of its existing customers as 33 months, and 55 months for the 56% who have stayed more than a year. Our reading: the first counts people who move in and the second those still there, so both can be true.

It also says about half its occupied space is used by customers who have been there less than 12 months. The SSA’s 2026 customer survey, of 232 customers, found 23.2% in their current unit for one to two years and about 39% for three years or more.

Our reading: churn tells you how fast the book turns over, and length of stay tells you how long a customer is worth keeping. A survey of current customers shows who has stayed, not how long a typical customer stays. Our customer guide sets out how stay differs for households and businesses.

StoreBay’s Customer retention report groups customers by the month they joined and shows how many from each month are still with you.

What do conversion, rate achievement and cost per move-in look like?

The SSA’s 2026 report puts enquiry conversion in 2025 at 60% for walk-ins, 51% for phone enquiries and 33.8% for email. In 2024 those were 69.7%, 57% and 25.1%. On 16 October 2026 we found no definition of conversion in it, and its 2025 report called that channel “online”, so treat a year-on-year move with care.

We found no UK ratio of achieved rate to asking rate on 16 October 2026 (we searched for “rate achievement”, “achieved rate”, “asking price” and “street rate” in the operator and SSA documents above). The nearest figure is Big Yellow’s: new customers over the year paid on average 0.7% less than the previous year’s move-ins and 6.9% less than customers moving out.

On 16 October 2026 we also found no published UK cost per move-in. Big Yellow speaks of improving the efficiency of its “cost per customer acquisition”, and on 16 October 2026 we found no figure for it. It gives marketing as a share of revenue, 3.7% in the year to 31 March 2026, and Safestore gives 4.1% of sales in its 2025 financial year and 4.2% in the half to 30 April 2026.

Big Yellow also says 35% of its paid-search clicks in that year came from searches for its own name. Our reading: a cost per click on its own is a weak stand-in for the cost of a customer, because brand searches and new-customer searches are mixed in it.

StoreBay’s Enquiries & conversion report counts the enquiries that came in during a period and how many have since moved in, grouped by how they got in touch, where they heard of you, the form they used or the site.

What about arrears, bad debt and move-ins?

Big Yellow’s bad debt expense was 0.2% of revenue in the year to 31 March 2026, and 81% of its customers pay by Direct Debit. Its receivables more than 45 days past due were £694,000 of £2.61 million, which is 0.33% of its £209.1 million revenue (our calculation). Safestore’s UK receivables more than 60 days past due were £0.7 million of £11.9 million, about 0.4% of UK revenue of £167.5 million (our calculation, from a figure given to £0.1 million).

On 16 October 2026 we found no arrears or bad-debt figure in the SSA’s 2025 or 2026 reports. Arrears are what is overdue today, aged debt is how long it has been overdue and bad debt is what you wrote off, so they answer three questions. Our late fees guide covers the law on late fees and interest.

The Arrears and Aged debt reports in StoreBay show what is overdue at each site, how much of the period’s billing was collected, and how old each debt is, in bands of 0 to 30, 31 to 60, 61 to 90 and over 90 days.

Big Yellow counts a move-in as a customer taking a storage room in a period and a move-out as a customer vacating one. Lok’nStore counted a move-in when goods went into the unit (annual report for the year to 31 July 2023). In the 2025 and 2026 documents we read on 16 October 2026 we found no UK move-in to move-out ratio and no move-in count.

The nearest figure is net absorption: Big Yellow’s occupied space grew 161,000 sq ft in the quarter to 30 June 2026, against 47,000 a year earlier. Its half-year results for 2017 to 2022 did print monthly counts, which our seasonality guide charts.

The Move-ins & move-outs report in StoreBay shows units let and units handed back side by side, by day, week or month, for any period up to two years, for all your sites or one. It counts units, not customers, so an occupier with two units counts twice.

Can you use published figures as a benchmark?

Treat them as a range of what is possible, not as a target. The SSA’s 2025 report counts container sites in its space total, 10.17 million of 64.3 million sq ft. The SSA says the gap between its all-store and mature-store figures reflects “the dilution effect of new supply entering at lower initial fill rates”.

Operators also describe different groups of stores. Safestore’s like-for-like stores are more than two years old and its mature stores more than five. Big Yellow’s same stores have reached 85% occupancy in an earlier year. The SSA’s mature stores have not opened or expanded in four years, and Lok’nStore counted stores over three years old.

The SSA’s 2026 report contradicts itself in places, so say which section a number comes from. It puts 2025 churn about 20 points below the pre-pandemic average in its text and about 27 in its panel, and it gives mature-store occupancy as 79.6% and as 80%.

A target is not a benchmark. Safestore says it expects stabilised UK like-for-like occupancy of 85% to 90%, against the 80.6% it achieved in its 2025 financial year. Our reading: compare a site with its own last twelve months first, then with sites of the same age and kind.

How should you write each KPI down?

Give each KPI a definition card that fits on one line: the name, the formula, what it divides by, which stores it counts, the unit (pounds a year or a week, with or without VAT) and the date it was taken. The table below does that for the twelve in this guide, with the published figure where there is one.

When two reports disagree, check the divisor before you check the data. A site that moves from 79.9% to 75.6% between two reports may not have lost a single customer.

Review the cards once a quarter and keep the old definition beside any new one for a year, so a trend line is never drawn across a change of method.

What does this guide not cover?

• Container and outdoor sites. The SSA’s space totals include container sites, and we did not separate them.
• Shurgard’s half-year results. We used its full-year 2025 release; we did not read its 2026 interim figures.
• Operators’ price pages. We read results and SSA reports, in which every price per square foot is annual; we did not check how operators quote prices to the public.
• Nations. The SSA splits its regions as English regions, Scotland and the West Midlands with Wales; on 16 October 2026 we found no split of UK figures by nation from Big Yellow or Safestore.
• Forecasts. This guide covers what is measured, not how to project it.

Sources

All read on 16 October 2026.

• Big Yellow Group’s results for the year ended 31 March 2026, 18 May 2026, with its glossary, its results presentation, and its Q1 trading statement of 20 July 2026.
• Safestore Holdings’ final results, 15 January 2026, its interim results, 11 June 2026, and its third quarter trading update, 3 September 2026.
• The Self Storage Association UK’s 2026 interactive report with Cushman & Wakefield, its 2026 industry report page and press release of 29 April 2026, and its 2025 annual report.
• Shurgard’s full-year 2025 results, 26 February 2026, and Lok’nStore Group’s annual report 2023, for the year to 31 July 2023.