Odds Formats

Three Formats, One Concept

SharpAPI returns odds in three formats simultaneously:


{
  "odds": {
    "american": -110,
    "decimal": 1.909,
    "probability": 0.5238
  }
}

American Odds

The standard in the US. Shows how much you win or must risk.

Odds	Meaning	$100 Bet Profit
-110	Risk $110 to win $100	$90.91
+150	Risk $100 to win $150	$150
-200	Risk $200 to win $100	$50
+200	Risk $100 to win $200	$200

Conversion formulas:


If negative: Decimal = 1 + (100 / |American|)
If positive: Decimal = 1 + (American / 100)

Decimal Odds

Standard in Europe/Australia. Shows total return per unit staked.

Decimal	$100 Bet Return	Profit
1.909	$190.90	$90.90
2.50	$250.00	$150.00
1.50	$150.00	$50.00

Tip: Decimal odds include your stake. A $100 bet at 2.50 returns $250 total ($150 profit + $100 stake).

Implied Probability

The market’s estimate of the outcome’s likelihood.


Implied Probability = 1 / Decimal Odds

Decimal	Probability	Interpretation
2.00	50%	Coin flip
1.50	66.7%	2/3 chance
3.00	33.3%	1/3 chance

Warning: Implied probability includes the bookmaker’s margin (vig). True probability is typically 2-5% lower.

The Vig (Juice)

Bookmakers build in a profit margin:


Fair coin flip: Both sides at 2.00 (50% + 50% = 100%)
With vig:       Both sides at 1.91 (52.4% + 52.4% = 104.8%)

The extra 4.8% is the bookmaker’s edge.

Converting Between Formats


// American to Decimal
function americanToDecimal(american) {
  return american > 0
    ? 1 + (american / 100)
    : 1 + (100 / Math.abs(american));
}
 
// Decimal to American
function decimalToAmerican(decimal) {
  return decimal >= 2.0
    ? (decimal - 1) * 100
    : -100 / (decimal - 1);
}
 
// Decimal to Probability
function decimalToProb(decimal) {
  return 1 / decimal;
}