What is my house worth? The four ways to find out

"What is my house worth" has no single answer, because value is not a property of a house. It is a prediction about what someone would pay, and different methods make that prediction differently, at wildly different costs.

There are four. Choose by what you need the number for.

1. An automated estimate, free

A model applied to whatever data the operator holds: past sales, tax records, an index, your own inputs. This site is one of these, and so is every portal estimate.

Accuracy: genuinely variable. The honest way to judge one is to ask what it knows. An estimate built from your actual purchase price and a repeat-sales index for your area has a real methodological basis. An estimate built from bedroom count and a regional average is a bracket wearing a number's clothing.

Use it for: orientation. Deciding whether to look into selling. Checking whether your equity is roughly where you thought. Tracking a trend over years.

Do not use it for: setting an asking price, arguing with a lender, a tax appeal, or a divorce settlement. It will not survive contact with any of those.

2. A broker or agent valuation, usually free

A local agent walks the property and prices it against what has recently sold nearby. In the US this is a broker price opinion or a comparative market analysis; in the UK it is a market appraisal.

Accuracy: good, and better than most people expect, because a decent local agent has information no model has. They know that the houses on the even-numbered side back onto the railway, that the school catchment boundary runs down the middle of the street, and what actually happened in the three sales that fell through.

The catch: it is free because it is a sales pitch. Some agents quote high to win the instruction, then talk you down after a few quiet weeks. The standard defence is to get three, discard the outlier, and ask each one to show you the comparable sales they priced from. An agent who cannot produce comparables is guessing.

3. A formal appraisal or surveyor's valuation, paid

A licensed appraiser in the US, or a RICS-registered valuer in the UK, inspects the property and produces a defensible written valuation.

Accuracy: this is the number that counts, in the specific sense that institutions accept it. A lender will lend against it. A court will consider it. A tax authority will engage with it.

Use it for: anything where money changes hands on the strength of the figure. Refinancing, probate, divorce, a tax appeal, a dispute.

It is the only option on this list that produces a number with standing, and it is worth the fee whenever the decision is larger than the fee, which is nearly always.

4. The market itself

List it and see. This is the only method that produces the actual answer rather than an estimate of it, and everything else on this list is a way of avoiding having to do it.

It is also the most expensive way to find out, because a failed listing is not free. A property that sits unsold and is then reduced carries a visible price history, and buyers read a reduction as a signal about the property rather than about the original pricing.

What actually moves your number

Whatever method you use, the same handful of factors do most of the work, and it is worth knowing which ones you can change.

• Location, which you cannot change. It dominates everything else. The same building costs multiples more in one postcode than another.
• Floor area, which you can sometimes change. Usable square footage or square metres is the strongest single physical driver, well ahead of room count.
• Condition, which you can change. Kitchens and bathrooms carry disproportionate weight because buyers price the cost and disruption of replacing them.
• Comparable evidence, which you cannot change but can understand. If three similar homes nearby sold recently, your range is narrow. If nothing has sold in eighteen months, nobody knows what your house is worth, including the agent.
• Tenure and legal quirks. In the UK a short lease can reduce value dramatically and is fixable at a cost. Anywhere, an access issue or a boundary dispute will surface at conveyancing and reprice the deal.

The practical order

Start with a free estimate to orient yourself. If it suggests the decision is worth pursuing, get two or three agent valuations and ask each for their comparables. If the decision involves a lender, a court, or a tax authority, pay for the appraisal. Do not skip straight from a free online figure to a major financial decision, and do not pay for an appraisal to satisfy idle curiosity.