Odds and Parlay Calculator

An odds calculator turns a price into a payout and a probability: enter the odds and your stake, and it shows the total return, the profit and the chance of winning the price implies. The parlay calculator does the same for several selections on one ticket by multiplying their decimal odds. The sections below explain betting odds step by step. Every worked example uses made-up prices for illustration only.

The three odds formats

• Decimal (1.57, 2.50): the total return for every $1 staked, including the stake. OLG, which uses this format on PROLINE+, puts it as Payout = Wager x Decimal Odds. A $100 bet at 1.57 returns $157: your $100 back plus $57 profit.
• American (-175, +150): common on North American sportsbooks. A minus number is the amount you risk to win $100; a plus number is what $100 wins. The minus side is the favourite.
• Fractional (3/2, 4/1): profit relative to stake, used mostly in British racing. 3/2 means $3 profit for every $2 staked.

Converting American and decimal odds

These formulas are what the converter runs behind the scenes:

• Positive American to decimal: (American / 100) + 1. Example: +400 becomes 5.00.
• Negative American to decimal: (100 / American without the sign) + 1. Example: -400 becomes 1.25.
• Decimal to American, when decimal is 2.00 or more: (decimal – 1) x 100, shown with a plus sign. Example: 2.50 becomes +150.
• Decimal to American, when decimal is under 2.00: -100 / (decimal – 1). Example: 1.571 becomes -175.
• Fractional to decimal: (top / bottom) + 1. Example: 3/2 becomes 2.50.

Worked example: a single bet

Example only, not a real line: you stake $20 on a team at +150. In decimal that is 2.50, so the total return is $20 x 2.50 = $50, of which $30 is profit. If you instead stake $50 on the favourite at -175 (decimal 1.571), a win returns $50 x 1.571 = $78.57, a profit of $28.57.

What implied probability tells you

Implied probability is the break-even chance built into a price: 1 divided by the decimal odds. The example price of 2.50 implies 40%; 1.571 implies 63.6%. If you think a team wins more often than its implied probability, the price looks generous to you; if less, it does not. Nobody knows the true probability, which is why a calculator can describe a price but never tell you whether a bet will win.

The margin hidden in every market

Add up the implied probabilities of every outcome in a market and the total is more than 100%. The excess is the overround, the sportsbook’s margin. In an example two-way market priced at -110 on both sides, each side converts to 1.909 in decimal, or 52.4%; together that is 104.8%, so the book keeps roughly 4.5% of the money staked on average. Markets with many outcomes, such as championship futures, usually carry a larger overround than a single game.

How the parlay calculator works

A parlay bundles two or more selections into one bet, and every leg must win. The combined price is the product of each leg’s decimal odds. OLG’s own example: a $100 parlay at combined odds of 15.00 returns $1,500.

Illustration with made-up prices: three legs at 1.91 each give 1.91 x 1.91 x 1.91 = 6.97. A $10 parlay would return $69.70. The catch is that each leg carries its own margin, and the margins compound. If each leg’s fair chance were 50%, the fair price for three legs would be 8.00, so the parlay pays about 13% less than fair odds, against about 4.5% on each single.

System bets spread one stake across several smaller parlays. On OLG’s example, $30 on a By 2’s system with three picks is split into three $10 two-team parlays, so one losing pick does not sink the whole ticket.

Pushes, voids and dead heats

When a whole-number line lands exactly, the bet is a push and the stake is returned. In a parlay, operators handle a pushed or void leg in different ways: most drop the leg and recalculate, but some lottery-style products treat an exact tie inside a combination differently. Read the sportsbook’s rules for the market. For sport-specific examples, see our guides to NHL odds and CFL odds.

A calculator is a tool for understanding prices, not a way to beat them. Betting is 19+ (18+ in Alberta, Manitoba and Quebec), and the licensed sportsbooks in your province are listed in our sports betting guide. If betting has stopped being fun, our responsible gambling page lists help in every province.