What is a bookmaker? How betting companies set odds and make money

A bookmaker is a company, or in older times a single person, that sets odds on the outcome of an event, takes bets on those outcomes, and pays out the people who bet correctly. The word gets shortened to “bookie”, and the business itself is often called a sportsbook when it operates online. Whether it is a global betting brand or a man with a chalkboard at a racecourse, the job is the same: price up every possible result, take money on all of them, and make sure the sums add up in the house’s favour over time. This guide explains what a bookmaker actually does, how it turns a profit, and how it differs from a betting exchange.

What does a bookmaker do?

The core task is pricing. Before a match or race, a bookmaker publishes odds for each outcome, and those odds are really a statement of how likely the firm thinks each result is, plus a built-in cushion for itself. Once the market is open it accepts stakes, keeps track of how much liability it is carrying on each side, and shifts the prices as money comes in. When the event finishes, it settles every bet, paying winners and keeping the stakes of everyone who got it wrong.

Modern online bookmakers do all of this across thousands of markets at once, from the match winner down to how many corners a football team will win or which batter tops the run charts. The scale is bigger than the old high-street shop, but the underlying trade has not changed since the first bookmaker chalked up a price.

How do bookmakers make money?

The answer is the margin, also called the overround or, in older betting slang, the vig. A bookmaker does not price a market at its true probability. It prices it slightly short, so that the implied chances of all the outcomes add up to more than 100 per cent. That extra slice is the profit it expects to keep over thousands of bets.

A worked example makes it clear. Take a two-way market, say a tennis match with two players who look evenly matched. A fair price with no margin would be 2.00 on each player, because a decimal price of 2.00 implies a 50 per cent chance and the two add up to a tidy 100 per cent. A real bookmaker will instead offer something like 1.90 on each. A price of 1.90 implies a 52.6 per cent chance, so the two sides together come to 105.2 per cent. That extra 5.2 per cent is the overround. It means that if the bookmaker takes balanced money on both players, it pays out less than it collects whoever wins.

The phrase for managing this is balancing the book. If bets pile up on one side, the firm shortens that price and lengthens the other to pull money the other way, trying to reach a position where it profits regardless of the result. It does not always get there, and a heavily backed favourite winning can cost a bookmaker on the day. Over a season and across every market, though, the margin is what keeps the lights on.

Bookmaker vs betting exchange

The key difference is who you are betting against. With a traditional bookmaker you bet against the house. The firm sets the price, takes the other side of your bet, and wins when you lose. A betting exchange works differently: it matches ordinary punters against each other, so one person backs an outcome and another lays it, and the exchange simply takes a small commission on the winnings. Because you can lay a result on an exchange, effectively acting as the bookmaker yourself, exchanges opened up bets that a fixed-odds firm never offered. We cover that model in full in our guide to what a betting exchange is.

Types of bookmaker

Most betting now happens with fixed-odds online sportsbooks, where the price you take is the price you are locked into when the bet is struck. Alongside them sit the traditional operators, the on-course bookmakers at a racecourse and the high-street shops that still trade in some countries. A smaller category is the spread-betting firm, which does not offer a simple win or lose bet but pays out based on how right or wrong you are, a riskier model that sits closer to financial trading than to a normal wager. For most people, a bookmaker means the fixed-odds sportsbook.

What separates a good bookmaker from a bad one?

A few things matter more than a flashy sign-up offer. The first is a licence from a recognised regulator, which is what forces a firm to hold customer funds properly and settle bets fairly. The second is the margin: a bookmaker running a tight overround gives better value than one padding its prices, and comparing the same market across a few firms shows the gap quickly. The third is the range and depth of markets, and the fourth is whether the firm pays out reliably and offers real responsible-gambling tools such as deposit limits and self-exclusion. Our betting site reviews look at operators against exactly these points.

Are bookmakers legal in India?

The legal position changed sharply in 2026. India’s Promotion and Regulation of Online Gaming Act, 2025, together with its 2026 rules, came into force on 1 May 2026 and placed a blanket prohibition on online real-money games, whether they turn on chance, skill or a mix of the two. In practical terms that restricts online real-money betting for operators aimed at India, while e-sports and social games sit in a separate, permitted category. Anyone reading about bookmakers from India should treat the topic as general information rather than an invitation to bet, and check the current rules where they are. We go deeper into the detail in our explainer on whether cricket betting is legal in India.

This article is general information about how bookmakers work, not betting advice or a recommendation to gamble. Online real-money gaming is restricted or prohibited in some places, including in India under the Promotion and Regulation of Online Gaming Act, 2025. Always check the rules that apply where you are. 18+.