How Sports Betting Odds Work

Sports betting has become one of the most popular forms of online entertainment among people in Africa. Any reliable online bookmaker—including Afropari, which is very popular in Francophone Africa—is a platform that allows users to bet on sporting events for entertainment or profit.

In addition to the bets themselves, bookmakers also offer odds. However, not all players clearly understand what this term means in the betting world. In this guide, we explain how sports betting odds work.

What are odds and what do they mean?

Sports betting odds represent the numerical estimate made by an online bookmaker regarding the probability of an outcome in a match.

Odds are usually expressed in decimal format with two digits after the decimal point. Each odd includes the bookmaker’s margin—meaning the profit the company makes regardless of the event’s outcome. The lower the odds, the higher the probability of the team winning, and vice versa.

The most common odds offered by bookmakers are 2.00. Players can bet on any event with such odds. For example, if you stake $200 and your prediction is correct and the team wins, your total return will be $400.

Odds formats: decimal, fractional, American

To properly understand odds, you need to know their formats. Each has its own features that are important to master. On sports betting platforms, the following formats are generally distinguished:

• Decimal odds (Africa/European). This is the most popular and widely used format in most countries. It’s expressed as a decimal number and indicates the total return if the player’s prediction is correct.

• American odds (+ / –). This format is widely used in the United States and appears with a “+” or “–” sign. The odds indicate the potential profit based on the stake. For example, with positive odds (+250), a stake of 100 units yields a net profit of 250 units. With negative odds (–150), you must stake 150 units to obtain a net profit of 100 units.

• Fractional (British) odds. This format is especially common in the UK and Ireland. The odds are expressed as a fraction, where the first number indicates the potential profit and the second indicates the amount staked.

With many bookmakers, you can choose the odds format that suits you best to make calculations easier.

Why do decimal odds dominate in Africa?

The largest African markets mainly use decimal odds on sports betting platforms. This trend can be explained by several reasons:

• Versatility and simplicity. Decimal odds are among the most popular formats because to calculate potential winnings, you simply multiply the odds by the stake amount.

• Globalization. Many international bookmakers are entering African markets. For them, it makes sense to keep the decimal format, which a large part of bettors are already used to.

• Regulation and local market specifics. The sports betting market in Africa is expanding rapidly, and national regulations are gradually evolving to regulate its development.

• Micro-betting. In Africa, small-stake bets placed at very high frequency are becoming increasingly popular.

With very high traffic in football and other popular sports, the decimal format helps attract new bettors and retain regular players.

Implied probability: quick calculation based on odds

Implied probability is the probability of an event calculated from the odds offered by bookmakers. It shows the probability the bookmaker assigns to an outcome while accounting for its margin.

It’s very easy to calculate the implied probability of decimal odds using this formula:

Probability (%) = (1 / odds) × 100

Examples:

• Odds 2.00 → 1 / 2.00 = 0.50 → probability 50%

• Odds 1.50 → 1 / 1.50 = 0.67 → probability 67%

• Odds 3.20 → 1 / 3.20 = 0.3125 → probability 31%

Decimal odds show how much the total stake increases if the bet wins.

Bookmaker margin: understanding the overround

The bookmaker’s margin (overround) is the bookmaker’s expected profit built into the odds. That’s why the sum of implied probabilities of all outcomes always exceeds 100%. The margin is the commission the player pays—not directly, but through odds that are slightly adjusted against them.

To make sports betting profitable, bookmakers set odds that differ from the true value. For example, suppose two teams have truly equal chances of winning (50% / 50%). Instead of offering fair odds of 2.00, the bookmaker offers 1.91 for each outcome. In this case, the bookmaker’s margin is about 4.5%.

If two bettors each stake $100 on opposite outcomes, the bookmaker will pay $191 to the winner and make a net profit of $9.

Comparing and converting odds: finding value

Comparing and converting odds across bookmakers is essential. It helps you:

• Find the most favorable odds on different platforms.

• Calculate implied probability.

• Determine the value of a bet.

• Understand the formats used by different online bookmakers.

Different odds formats represent the same information, but in different numeric forms.

Decimal odds show how many times your stake is multiplied. Implied probability is calculated as:

P = 1 / decimal odds

British fractional odds show the ratio between potential profit and the initial stake.

Example: if the odds are 5/2, implied probability is calculated like this:

2 / (5 + 2) = 2/7 = 28.57%

Pan-African examples (football, AFCON, local leagues)

To understand the calculation and conversion of odds, it’s useful to look at a few practical examples:

• Africa Cup of Nations match between Nigeria and Cameroon. Bookmakers offer odds ranging from 2.30 to 2.55 for a Nigeria win, 2.85 to 2.90 for a draw, and 3.00 to 3.10 for a Cameroon win. Comparing decimal odds: one bookmaker offers 2.55, which is higher than 2.30 and therefore clearly more advantageous. Next, calculate implied probability. For 2.30, it’s 43.5%, and for 2.55, it’s 39.5%. The difference is significant. This could already represent a value-bet opportunity if the bettor estimates Nigeria’s true win probability exceeds 45%.

• Again Nigeria vs Cameroon: totals market. Over is offered at 2.05 and under at 1.85. For over: 1 / 2.05 = 48.78%. For under: 1 / 1.85 = 54.05%.

As you can see, the principle is quite simple, even if it may seem complicated at first glance.

Common mistakes and best practices

Before betting on sports with bookmakers, it’s important to keep several recommendations in mind to avoid frequent mistakes:

• Don’t confuse “payout” and “profit.”

• Take the bookmaker’s margin into account.

• Check the odds before confirming a bet.

It’s also important to monitor your bankroll management to avoid heavy losses on your bets.

Quick conversion table

FAQ – additional example questions

How does a decimal odd of 2.35 work in practice?
You just multiply the stake amount by 2.35. For example, a stake of 100 units will produce a total payout of 235 units (i.e., a net profit of 135).

How do you calculate implied probability from odds?
You divide 1 by the available decimal odds. Formula: Probability (%) = 1 / odds × 100.

Why do two African platforms sometimes show large differences in odds for the same match?
Each bookmaker independently evaluates the teams’ chances, relying on different sources: statistical data, current player form, expert analysis, betting volume, etc.

What is a bookmaker’s “margin” and how do you determine it?
The margin is the commission built into the odds to guarantee a profit regardless of the outcome.
By adding up the implied probabilities of all outcomes in a market (for example: win–draw–loss), you generally get more than 100%. The amount above 100% corresponds to the bookmaker’s margin.

Do odds change faster in Africa for very popular matches?
Yes. As everywhere else in the world, odds for heavily followed matches move faster due to the large betting volume and new information.