What our rent numbers mean — and what they don’t

Asking rents, not agreed rents

Every figure on these pages comes from live listings — what landlords and letting agents are advertising. It is not what the tenant finally agreed to pay. Those figures do exist: the ONS publishes an index of achieved private rents. But it arrives with a lag and at a much broader geography than a single postcode district.

Asking rents are the honest proxy. They move first, because they are the market’s opinion of itself before anything is signed, and they are specific enough to say something useful about one postcode. In a tight market, homes go for the asking price or above it; in a slack one, they go below. Treat our median as the top of the conversation, not the end of it.

Time on the market measures advertising, not emptiness

When we say the typical home in a district has been listed 24 days, we mean the advert has been live for 24 days. That is not the same as the property standing empty for 24 days, and we want to be direct about the gap.

Adverts often stay up while referencing goes through. A property that falls through and is relisted starts its clock again. Neither of those is anyone behaving badly — it is simply how listing feeds work. The practical effect is that this measure will tend to overstate how long homes actually sit empty.

So read it as a demand signal, which is what it is good for. Rising days-listed means stock is accumulating and you have room to negotiate. Falling days-listed means you need to move quickly. It is not a void period, and we will not present it as one.

We only publish where we have enough to be honest

A postcode district gets a page only when it clears two bars:

• At least 20 active listings in the most recent week. A median drawn from five flats is not a market read, it is an anecdote.
• At least four weeks of history, so there is a trend to speak about rather than a single point.

Below either bar we publish nothing at all. That is why a district you would expect to see may be missing — it is a coverage gap, not a claim that nothing is for rent there.

We also withhold a district whose median falls outside a plausible range, as a guard against a bad price parse reaching the page. It occasionally catches a genuinely expensive district by mistake. We would rather be quiet than wrong.

Updated every Monday

We take a snapshot each Monday morning and the pages rebuild from it. Each week’s figure is a photograph of what was advertised that morning — not a rolling average, and not revised afterwards. The week stamp on every page tells you which Monday you are looking at.

Weeks marked “est.” are reconstructed from our listing history rather than captured live. They are approximate, we label them as such wherever they appear, and the trend firms up as fresh weeks accrue.

Where the geography comes from

We report by postcode district — the outward half of a postcode, like SW15 or M4 — because it is the smallest area most people can picture and it is stable over time.

Postcode district names, coordinates and city groupings contain OS data © Crown copyright and database right, used under the Open Government Licence v3.0. City groupings follow the everyday sense of a city rather than a formal boundary: Greater London districts are grouped as London, while separate towns such as Slough and Watford stand on their own.

Quoting the Letty Rent Read

These pages are free to read, free to quote and free to link. There is no paywall and no registration, and that is deliberate — a number nobody can check is not worth publishing.

If you are writing about a local market, cite it as “Letty Rent Read, {month} — methodology at lettyapp.io/rents/methodology” and link back to the district page you took the figure from, so your readers can see the same week stamp you did.

If a number looks wrong to you, we would rather hear it than not: hello@lettyapp.io.