How Does Gambly Calculate a Bet’s Edge?

While Gambly doesn’t take a direct stance on games, we do calculate the edge–or expected ROI–for most bets.

In simple terms, these calculations are a comparison of the current line on a bet at any given sportsbook and the consensus of market-making sportsbooks, which we then adjust based on factors such as historical range of outcomes to provide edges on a vast array of derivatives and alt markets.

We don’t take a viewpoint on games outside of market data, meaning this approach is top-down and sport-agnostic. For example, if DraftKings has the odds of a certain event at -110 and all other books are at -120, it’s likely that DraftKings’ line is off. But not all sportsbooks are created equally–some are sharper than others–and we use a weighted combination of each market-making book’s historical accuracy to calculate what the actual vig-free line should be, or the true odds. These formulas are sport-specific, meaning the “source of truth” for baseball is different than basketball, for example.

By comparing the current odds to a probable “true line” based on current market structure, it’s possible to calculate a bet’s expected ROI. If the vig-free true line based on market-making books is even money and FanDuel has that bet at +110, we can calculate the anticipated edge (even money is of course a coin flip, and getting paid +110 on each bet equates to a 5% edge).

There’s some nuance to how the “true line” is calculated–certain sportsbooks get different weights, adjustment for recent line movement, and so on–but in a nutshell, that’s how things work. A pure data-driven approach analyzing:

current market structure (the odds across all sportsbooks in real-time)
historical accuracy of each sportsbook for each sport
derivatives: comparing -6.5 (-110) to -7 (+105) in NFL, for example

How are Gambly's edges different (and better)?

Derivatives are betting markets that are related to the three main markets. This includes a wide range of potential bets, including things like first-half and first-quarter bets, alternative spreads and totals, and so on. Sportsbooks typically derive these numbers using historical models and the current numbers on the main markets.

Pricing these markets can be quite difficult…

Should you bet an NFL favorite at -1 (-115) against the spread or at -125 on the moneyline? Should you bet a player over 68.5 yards at -110 or over 74.5 yards at +130? How do these answers change if the total is 38.5 versus 51.5?

When looking at alt markets, how do you know which of the many different spreads and totals is mathematically the best option?

Gambly provides you with the expected ROI on all derivatives and alt markets, letting you compare lines across different markets.

This process is also important for comparing spreads and totals, which are often different across sportsbooks. How often do you see the exact same spread or total across every sportsbook? It’s pretty rare. It’s absolutely pivotal to know if you should be betting over 46.5 (-110) or over 47 (+100).

Why this is so important

Comparing various forms of bets is essential to being profitable because nearly every bet offered is a derivative of a main market. Building these models to compare apples-to-oranges bets is extremely difficult but absolutely necessary to get the highest edge.

If you want to bet the over on Dak Prescott's passing yards, are you better off betting over 245.5 (-118) at Underdog or over 248.5 (-112) at DraftKings?

Even within a single sportsbook, you need to determine which alt lines are best. At DraftKings alone, I'm currently looking at 27 different milestone props for Prescott's passing yards. Maybe 260+ yards (+115) is best? Or is it 270+ yards (+143)? Or maybe it's actually 230+ yards (-176)?

The thing is, there's an answer to these questions, but it's a difficult one to uncover. We've put the resources into the data science behind these comparisons, so we know that if Prescott's median "true line" projection should be, say, 246 yards, then he has a certain knowable probability of going over 250 yards, 280 yards, and so on–based on a multitude of factors including historical range of outcomes, game specifics like the total and spread, etc.

The reality is that nearly every bet you make needs to be compared to other slightly different versions, and calculating which are best is an incredibly difficult task. We've put the time and energy into doing that–using real models built by pro bettors–which is what makes Gambly's edges unique. We're not treating 4.5-point and 5.5-point spreads the same. We're not treating over 243.5 yards as automatically better than over 247.5 yards just because the number is lower (it depends on the payout).

We're not just guessing.

There are lots of edge calculations out there. By and large, they make no such line adjustments (or, at best, inaccurate ones) because, simply put, it's very difficult to do. Gambly does the hard part for you.

The goal is to create pro-level tools that anyone can use. We hope to distill all the complexities of what goes on behind the scenes into straightforward numbers shown in an extremely simple-to-use app.

What's so great about top-down betting?

There are a multitude of ways to make profitable bets, all of which ultimately come down to determining the “fair price” for a bet and uncovering situations when sportsbooks are most off from that number.

Top-down betting is the optimal path for almost all bettors, though, because it allows one to leverage the cumulative knowledge of other smart bettors. When Pinnacle–a sharp sportsbook that takes action from the best gamblers–moves a line to -115 and FanDuel is still at even money, it signals that Pinnacle has information (likely from a sharp bettor) that signals even money at FanDuel is probably now a good bet.

The benefits of top-down betting include:

Timeless–no need to continually update a model and worry if it’s still beating the market
Ability to leverage the work of sharp bettors
Far larger pool of available bets (albeit at a smaller edge)
More bets, less bankroll variance
A higher degree of confidence in being on the right side
Can be used in combination with a bottom-up handicapping approach

The reality is that almost all bettors are better off starting with a top-down approach and then searching for the bets which are most intriguing to them based on personal factors, which is exactly what Gambly is built to help you do.

In a Nutshell

Gambly's edge calculations are among the most accurate you can find because of our commitment to data science and integrity.

We use real-time data.

We continually refine our process to improve our calculations.

We form accurate "true lines" based on many sport-specific data points.

We can accurately compare apples-to-oranges bets in a way that others cannot do–such as knowing when to bet -7 vs. -6.5 or over 38.5 instead of over 38–because of our commitment to accurate data science.

In a nutshell, we take a lot of pride in our edge calculations; the aim is to remove all of the complex and challenging work behind the scenes so you can make profitable bets as efficiently as possible.