What is an Alternative Lines Calculator?

The Alternative Lines Calculator is a free sports betting tool for U.S. bettors that shows fair prices and true probabilities for alternate spreads or totals. Enter the main market line (for example, "Lakers -7.5") and its vig-free odds from any sportsbook—like FanDuel, DraftKings, BetMGM, or BetOnline—and it automatically outputs the fair American odds for every alternative line. You’ll see what the line should be priced at, without the built-in sportsbook margin.

How do you calculate an alternative line?

It depends on the sport. For basketball spreads, the calculator uses historical data and treats the point spread as a threshold in a Normal distribution of final scoring margins. Your vig-free probability anchors the mean of that distribution. From there, it shifts the line up or down in 0.5-point increments, recalculating the fair chance of covering each alternate spread. This approach works for NBA, WNBA, and other high-scoring sports.

How does vig affect the calculation?

The calculator requires vig-free odds as input—meaning the sportsbook’s margin must be removed first. For example, if both sides of a market are "-110", you’d convert that to a no-vig probability before entering it. This ensures the calculator reflects true fair odds, not prices padded by the house edge. If you use vig-included prices from sportsbooks like FanDuel or Caesars, the model’s results will be slightly biased toward the book.

How does the league or sport affect alternative lines?

Different leagues produce different scoring spreads and variances. NFL games have much larger margin volatility than NBA or WNBA games. Our calculator uses a Normal distribution tuned specifically to WNBA scoring data but will soon include custom standard deviations for NFL, NBA, MLB, and NCAA markets to better match each league’s scoring profile.

Do totals (over/under) affect alternative spreads?

Yes. The total points line affects how much scoring variance to expect. Higher totals mean wider possible outcomes, which changes the fair prices for alternate spreads. Currently, the calculator uses a fixed standard deviation per sport for simplicity, but future versions will adjust dynamically based on the game total to reflect scoring volatility more precisely.

How accurate are the results?

They’re mathematically accurate given the model’s assumptions, and they closely approximate fair market prices when vig is removed. However, real sportsbook lines also reflect public betting patterns, lineup changes, and liquidity, so minor differences are normal. Use the calculator as a reference to identify value and compare whether alternate lines on U.S. sportsbooks like FanDuel, DraftKings, or BetMGM are fairly priced.

Bettor Ed Alternative Lines Calculator

Enter the Sport, Spread, and Vig-Free Price to get Alternative Line prices

Frequently Asked Questions

Find answers to commonly asked questions about the Alternative Lines Calculator

What is an Alternative Lines Calculator?
- The Alternative Lines Calculator is a free sports betting tool for U.S. bettors that shows fair prices and true probabilities for alternate spreads or totals. Enter the main market line (for example, Lakers -7.5) and its vig-free odds from any sportsbook—like FanDuel, DraftKings, BetMGM, or BetOnline—and it automatically outputs the fair American odds for every alternative line. You’ll see what the line should be priced at, without the built-in sportsbook margin.

How do you calculate an alternative line?
- It depends on the sport. For basketball spreads, the calculator uses historical data and treats the point spread as a threshold in a Normal distribution of final scoring margins. Your vig-free probability anchors the mean of that distribution. From there, it shifts the line up or down in 0.5-point increments, recalculating the fair chance of covering each alternate spread. This approach works for NBA, WNBA, and other high-scoring sports.

How does vig affect the calculation?
- The calculator requires vig-free odds as input—meaning the sportsbook’s margin must be removed first. For example, if both sides of a market are -110, you’d convert that to a no-vig probability before entering it. This ensures the calculator reflects true fair odds, not prices padded by the house edge. If you use vig-included prices from sportsbooks like FanDuel or Caesars, the model’s results will be slightly biased toward the book.

How does the league or sport affect alternative lines?
- Different leagues produce different scoring spreads and variances. NFL games have much larger margin volatility than NBA or WNBA games. Our calculator uses a Normal distribution tuned specifically to WNBA scoring data but will soon include custom standard deviations for NFL, NBA, MLB, and NCAA markets to better match each league’s scoring profile.

Do totals (over/under) affect alternative spreads?
- Yes. The total points line affects how much scoring variance to expect. Higher totals mean wider possible outcomes, which changes the fair prices for alternate spreads. Currently, the calculator uses a fixed standard deviation per sport for simplicity, but future versions will adjust dynamically based on the game total to reflect scoring volatility more precisely.

How accurate are the results?
- They’re mathematically accurate given the model’s assumptions, and they closely approximate fair market prices when vig is removed. However, real sportsbook lines also reflect public betting patterns, lineup changes, and liquidity, so minor differences are normal. Use the calculator as a reference to identify value and compare whether alternate lines on U.S. sportsbooks like FanDuel, DraftKings, or BetMGM are fairly priced.