El Apuestón — Plain-English answers about odds, house math, and how regulated gambling works

Plain-English answers about odds, house math, and how regulated gambling works

Odds Format Reference Table

The same bet can be written as fractional odds (5/1), decimal odds (6.00), or a moneyline (+500). This table lays the three formats side by side, along with the implied probability each price represents and what a $10 stake would return in total if the bet won. Every figure here is an arithmetic identity that follows from the definitions of the formats — decimal odds are the fractional odds plus one, implied probability is one divided by the decimal odds, and the moneyline restates the same ratio against a $100 reference stake. Nothing in this table is an estimate.

This table converts between notations; it says nothing about whether any bet is good value. The implied probability of a bookmaker's price is not the true probability of the outcome — posted prices include the operator's margin, so the implied probabilities across all outcomes of an event sum to more than 100 percent. This site does not provide betting, financial, or legal advice.

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Fractional ▲	Decimal	Moneyline	Implied probability	Total return on $10 win
1/1 (evens)	2.00	+100	50.0%	$20.00
1/2	1.50	-200	66.7%	$15.00
1/5	1.20	-500	83.3%	$12.00
10/1	11.00	+1000	9.1%	$110.00
2/1	3.00	+200	33.3%	$30.00
20/1	21.00	+2000	4.8%	$210.00
4/5	1.80	-125	55.6%	$18.00
5/1	6.00	+500	16.7%	$60.00
6/5	2.20	+120	45.5%	$22.00

El Apuestón — Spanish for "the big bet" — is a small reference site about how gambling actually works on paper: how to read the three common odds formats, what the house edge is and where it comes from, why a bookmaker's odds always add up to more than 100 percent, and how licensed gambling is regulated and verified in the United States and the United Kingdom.

None of this is betting advice. The site takes no position on whether you should gamble, and it doesn't pick games, systems, or operators. What it does is explain the arithmetic and the institutions, because both are knowable and most of what circulates about them online is muddled. Every number on this site is either simple arithmetic you can check yourself or a claim tied to an official source.

The most-used thing here is the odds format reference table, which lays out fractional, decimal, and moneyline odds side by side with the implied probability each one represents — useful whenever you're reading about betting and the formats don't match.

There is also an honest page of help and support resources listing the established organizations — the National Council on Problem Gambling, Gamblers Anonymous, and others — for anyone whose gambling has stopped being entertainment. We keep that page current because a reference site about gambling that omits it isn't doing its job.