Key takeaways

• Definition: an arb is a pair of opposite bets on a two-way market whose implied probabilities add up to less than 100%, so the stakes return the same amount whichever side wins.

• NBA markets: spreads, totals and moneylines all work, since an NBA game can’t end in a tie. Player props and live lines also produce arbs, with more rules to match and less time to act.

• Cost: a -110/-110 market adds up to 104.76%. A pre-game straight trade on Novig carries no fee, so a 50-cent leg costs exactly 50% and the other side only needs a plus price.

• Risks: both legs must grade on the same rules, prices can move between bets, and sportsbook house rules let a book lower an account’s limits.

• Tools: arbitrage scanners compare prices across many apps at once. Check which apps a scanner covers before you rely on it.

How NBA arbitrage betting works

NBA arbitrage betting means backing both sides of the same market at two different places, at prices that guarantee the same return either way. It happens when two places don’t agree on the price. Convert each price to an implied probability and add the two. If the total is under 100%, there’s an arb; above it, the two margins have closed the gap.

Every point of vig or fee on a leg is a point the two prices have to disagree by before an arb exists. Among prediction markets, Novig’s pre-game straight trades carry no fee for either side, so a 50-cent contract is a true 50% leg. The app isn’t available in Arizona, Michigan or Nevada, and its Ohio status is unsettled after a state cease-and-desist letter. Kalshi and Polymarket charge takers on every trade, and ProphetX takes 2% of net winnings on straight trades. Sportsbooks usually supply the other side, since each book sets its own prices.

Where arbs show up in NBA markets

Spreads and totals

Both legs have to be on the same number: one team -3.5 against the other +3.5, or over 224.5 against under 224.5. Half-point lines can’t push, which keeps the payout identical on both legs. A whole number such as -4 can push at one place and lose at the other if the lines don’t match exactly.

Moneylines

An NBA game always has a winner, so the moneyline is a two-way market with no draw to cover. Check that both places count overtime, as most full-game rules do.

Player props

A prop is over/under on one player’s stat line, and the lines move on injury and minutes news. At most sportsbooks a prop is void if the player never takes the court, and another platform’s rules may grade the same contract differently. Read both before you bet a prop arb, since they don’t always agree. The NBA player props guide covers how those lines are set.

Live lines

NBA prices change on almost every possession, so a live arb can disappear between the first bet and the second. Live trades on prediction markets carry taker fees, including on platforms that charge nothing before tip-off.

A worked NBA arbitrage example

The prices below are an example, not current lines. Say a sportsbook lists Team A -3.5 at +105, and on a prediction market Team B +3.5 trades at 50 cents as a pre-game straight trade with no fee.

Whichever team covers, one leg returns $200 on $197.56 staked, a $2.44 profit, or 1.23%. To size the stakes, divide the target return by each leg’s decimal odds. Here that’s $200 / 2.05 for the sportsbook and $200 / 2.00 for the contracts.

The same pair with fees on the second leg:

• Kalshi taker at 50 cents: $3.50 in fees on 200 contracts, total outlay $201.06, a $1.06 loss.

• Polymarket taker at 50 cents: $3.48 in fees, a loss of about $1.04.

• ProphetX at +100 with 2% of net winnings: $2.44 profit if Team A covers, 44 cents if Team B covers.

• A second sportsbook at -110 on Team B: 52.38% plus 48.78% is 101.16%, so there’s no arb.

• The same contracts taken live: $3.00 in fees, total outlay $200.56, a 56-cent loss.

Why a no-fee leg widens the window

At -110 on both sides, each side implies 52.38%, and the two add up to 104.76%. For an arb between two sportsbooks, one book has to price a side longer than +110 when the other book is at -110 on the opposite side.

Against a 50-cent leg with no fee, any plus price on the other side is an arb. Against a 50-cent taker leg on Kalshi, which costs 51.75 cents with the fee, the other side has to be +108 or longer.

A maker who posts a price and waits for a fill pays no fee on any Novig trade type, which helps on live and futures legs too, though a resting order may not fill before the other price moves. The size available at any price is whatever other users have posted, so a large arb may only partly fill.

Risks in NBA arbitrage

Price moves

If the second leg is gone by the time you place it, you’re holding a one-sided bet at an average price. Place the leg that’s most likely to move first.

Mismatched rules

Push rules on whole-number lines, prop voids and overtime treatment all decide whether the two legs settle as a pair.

Stake limits

Sportsbook house rules let a book lower an account’s limits, DraftKings’ among them, and arbitrage tools say in their own FAQs that frequent arbing can lead to limits.

Money in several places

An arb needs funded accounts on both sides before the prices appear. Deposits can carry costs: Kalshi charges up to 2% on card deposits, for example. Winnings can be taxable, so keep records of both legs.

Arbitrage tools

Arb scanners pull prices from many apps, flag pairs that add up to less than 100% and size the stakes. OddsShopper’s finder, for one, says it scans more than 110 sportsbooks and puts live arbs on its higher-priced plan. Check whether a scanner includes the prediction markets you use, since a no-fee leg it can’t see is an arb it won’t show. Current NBA prices are on our NBA odds page, and the NBA spread, moneyline and totals guide covers converting American odds to probabilities.

FAQ

What are the best platforms for arbitrage betting?

You need at least two places with different prices on the same market, and the cheaper each leg, the more arbs exist. On a pre-game NBA leg, Novig’s straight trades carry no fee for either side. Sportsbooks such as DraftKings and FanDuel usually supply the other side, and the best NBA betting apps guide compares them.

What is the best prediction market for arbitrage betting?

Fees decide it, since every cent of fee is price gap the two legs have to cover. Kalshi’s and Polymarket’s taker fees, about $1.75 per 100 contracts at 50 cents, close many small arbs, and ProphetX’s 2% fee on net winnings trims the margin. A pre-game no-fee leg on Novig needs only a plus price on the other side.

Is arbitrage betting legal?

Yes, where betting itself is legal. You’re placing ordinary bets or trades on licensed or federally regulated platforms.

How much can you make from an NBA arb?

Most arbs return a small slice of the total stake, and that’s the whole profit. The example above returns 1.23%, and OddsShopper puts typical arbs at around 1% to 5%.

Do sportsbooks limit arbitrage bettors?

Their house rules allow it. DraftKings, for one, can lower a customer’s maximum payout limit at its discretion, and arbitrage tools warn their users that frequent arbing can lead to limits.

Responsible gambling

21+. Gamble responsibly. If betting stops being fun, call or text the National Problem Gambling Helpline at 1-800-MY-RESET (1-800-697-3738), or visit ncpgambling.org.