Odds Conversion Guide: Fractional, Decimal and American

Conversion formulas

These are payoff transformations. DraftKings provides one operator reference showing the three formats.

Worked conversion: 5/2

1. Convert to decimal: 5 / 2 + 1 = 3.50.
2. Convert decimal to positive American: (3.50 - 1) x 100 = +250.
3. Verify with 100 units: both 5/2 and +250 produce 250 units profit and 350 units gross return.

Worked conversion: -150

1. Use the negative-American formula: 100 / 150 + 1 = 1.6667.
2. Decimal profit per unit is 1.6667 - 1 = 0.6667.
3. The exact fractional form is 2/3, subject to display rounding.

Common reference prices

Verification checklist

• Compare profit on the same stake, not the printed numbers.
• Preserve enough decimal places during calculation and round only for display.
• Check the sign on American odds before choosing the formula.
• Treat approximate fractional displays as rounded representations when the decimal converts to a repeating fraction.

Use payoff as the conversion invariant

An odds conversion is correct when each format produces the same profit on the same stake. Suppose decimal odds are 1.80. Decimal profit on 100 units is 100 x (1.80 - 1) = 80 units. The fractional form is 4/5, which gives 100 x 4 / 5 = 80. Because the decimal price is below 2.00, the American formula is -100 / (1.80 - 1) = -125. Risking 125 units at -125 produces 100 units profit, which is the same 0.80 profit per unit.

This invariant is more reliable than comparing how large the printed numbers look. +200, 2/1 and 3.00 appear unrelated but all produce two units profit per unit staked. Conversely, -200 is 1/2 and 1.50, not 3.00.

Handle display rounding explicitly

Some exact decimal prices become repeating fractions or American values. Decimal 1.91 converts to fractional profit ratio 0.91 and American odds of about -109.89. An interface may display 10/11 or -110, each of which is close but not identical. When accuracy matters:

• retain the accepted format and price from the receipt;
• label converted displays as approximate;
• compare expected returns using the original accepted price;
• do not infer that two rounded labels guarantee identical settlement.

Conversion changes the notation, not the event, market definition or probability evidence.

Related resources

Continue with calculating betting returns or implied probability.

Continue learning

• Next guide: Accumulator Odds
• Related guide: Ante-Post Odds
• Definition: American Odds

Assumptions and limitations

The table assumes standard fixed-odds payoff conventions and no commission or deductions. A converted price preserves the payoff but does not make differently defined markets comparable.