Vig (margin)
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Enter both sides of a 2-way market, or all three sides of a 3-way, and see how much of the total handle the book keeps: the hold percent, the vig, and the overround. The standard -110/-110 line works out to a 4.55% hold. It recomputes live as you type.
| Outcome | Your price | Decimal | Implied probability |
|---|
Comparing holds across books? That is line shopping, and it is the whole reason ParlayAPI exists: the API returns the same market priced by 30+ sportsbooks in one response, so you can compute the hold at every book and bet where it is lowest. Pull live odds for these calculations with a free API key, or read the docs.
Every price implies a probability: p = 1 / decimal odds. A fair
market's probabilities would sum to exactly 100%. A real book prices every
outcome a little short, so the sum (the overround) lands above 100%.
The hold is that overpricing expressed as a share of the total money wagered.
Each -110 side implies 110 / 210 = 52.38%, so the overround is
104.76%. The vig is 4.76%, and the hold is
0.0476 / 1.0476 = 4.5455%, shown here as 4.55%. The sanity check is
cash flow: with balanced action the book collects 110 + 110 = 220 and pays the
winner 210, keeping 10, and 10 / 220 = 4.5455%. You will often see
this quoted as 4.54%; that is the same number truncated instead of rounded.
Both describe the same edge. Vig measures it against a fair 100% market
(overround - 1), hold against the actual money collected
((overround - 1) / overround). Since the overround is above 1, the
hold is always slightly smaller than the vig. If someone quotes "4.76% on a
standard NFL spread" they mean the vig; "4.55%" (or the truncated "4.54%") means
the hold. To see where the margin sits on each individual outcome, run the same
prices through the no-vig calculator,
which removes it and returns the fair odds.
Hold is the share of total money wagered on a market that the book expects to keep when the action is balanced. It exists because the implied probabilities of the posted prices sum to more than 100%. Formula: hold = (overround - 1) / overround.
Vig (or margin) is overround - 1: how far the implied probabilities exceed 100%. Hold is the same edge divided by the overround, so it reads as a share of the handle. On -110/-110 the vig is 4.76% and the hold is 4.55%. Quote either, but do not mix them.
Exactly 1/22 of the handle: 4.5455%, displayed here as 4.55%. The book collects 220 with balanced action and pays back 210, keeping 10, and 10/220 = 4.5455%. Many write-ups quote 4.54%, which is the same number truncated.
Within one book, almost never: a negative hold means the implied probabilities sum below 100%, so staking every outcome in proportion locks in a profit. Across different books it happens all the time, and finding those combinations is what the arbitrage calculator checks.