How does Bytky know if a flat is a good deal?

A listing someone looking at this one would weigh it against. For a flat, Bytky keeps only listings that match on every count below, then takes the nearest. The same flat advertised on both sites counts once.

• The same offer and kind of property: rentals with rentals, flats with flats.
• A usable size within 25% either way: a 60 m² flat compares with flats of 45 to 75 m².
• One room more or fewer: a 2+kk compares with one-, two- and three-room flats.
• Live now, or taken down in the last 90 days, at its last asking price.

Houses follow the same idea with wider margins: a floor area within 30%, cottages kept apart from family houses, and the plot weighed in.

As close as it can. For a flat, Bytky searches within 500 m first, then 1 km, then 2 km, then the whole municipal part, and stops at the first ring that holds 12 comparables. It uses the nearest 20 at most and lists every one of them, so the estimate can be checked by hand.

Houses search wider: 1 km, 3 km and 6 km, then the municipality, then the okres up to 25 km away. The card says how many it used and how far it looked: ‘Based on 20 similar flats within 800 m’.

From each comparable's price per m², weighted by how alike it is, then multiplied by this listing's size. The fair price is the weighted median. The typical range runs from the weighted 25th to the 75th percentile: the middle half of the comparables.

• Distance: a comparable 1 km away counts half as much as one next door (3 km for houses).
• Recency: one taken down 90 days ago counts half as much as a live one.
• Condition: the same condition counts fully, one step apart three quarters, further apart half.
• Lift and floor: a different lift, or a floor more than three apart, counts a little less.

Prices far outside the rest, such as a short-term let priced per night or a garage filed as a flat, are dropped before the median is taken. No building or advertiser can fill the set: at most 3 comparables come from one building and 4 from one advertiser.

The Fair price card adds a negotiation room line, low, some or high, with its reasons listed. It's built from facts about the asking price and its history, never advice:

• How far the ask sits above or below the fair price.
• How long it has been on the market, against its comparables.
• Whether its price has already been cut, and whether it was listed before.
• How many similar listings cut their price, and by how much.

A flat asking 10% over the fair price that has sat twice as long as its neighbours, with a price cut behind it, reads high. One just listed below the fair price reads low.