House offer calculator

The short answer: a useful offer calculator doesn't just take a percentage off the asking price — that only anchors you to the seller's number. It works from what comparable homes have actually sold for, adjusts for how the market has moved, and factors in how long the property has been listed. That's the difference between a guess and an offer you can defend.

Why most "offer calculators" mislead

Plenty of tools ask for the asking price and subtract a fixed percentage. The problem is baked in: the asking price is the seller's marketing figure, so anything derived from it inherits their optimism. Take 10% off an overpriced home and you're still overpaying — just by less. A calculator worth using starts from independent data, not from the number the estate agent chose.

What a good offer calculator actually does

It answers three questions in order:

1. What's the home worth? Built from comparable sold prices nearby — same type, same size — adjusted to today's value.
2. Where should you open? A credible opening offer that leaves negotiating room without being dismissed.
3. Where's your ceiling? The walk-away number, decided before emotion takes over.

How HouseOffer works it out

Paste a property link and HouseOffer pulls comparable completed sales from HM Land Registry, adjusts them to today using the ONS House Price Index, checks how long the property has been on the market, and returns an independent view of value plus a recommended opening offer. No spreadsheet, no percentage-of-asking shortcut — the actual evidence, in about a minute.