Share this

Wizard Recommends

Last Updated: September 23, 2018

Betting on the NBA

Introduction

This page addresses betting on basketball, specifically the NBA. The figures in this pages are based on 6,567 historical games, from seasons beginning 2013 to 2017. It is assumed the reader knows basic sports betting terminology. If this is not the case, please visit my page on sports betting first.

Betting Against the Spread

On average, the home team wins 58.4% of the time and scores 2.70 more points than the road team. However, betting against the spread, I show road teams to be the much better value, as the following table shows. The table is based on laying 11 to win 10. The return column shows the expected percentage of money won (or lost when negative) to money bet. As you can see, betting home teams has a house edge of 6.22%, while road teams are only 2.70%.

Road or Home Team Against the Spread

Side Wins Probability Return
Road 3,280 0.499467 -0.026981
Home 3,159 0.481042 -0.062157
Push 128 0.019491
Total 6,567 1.000000 -0.044569

The next table shows the results betting on underdogs and favorites against the spread. This does not include the 61 games where the point spread was zero. I was expecting underdogs to do significantly better, but the results proved me wrong — they did only slightly better. As you can see, the probability of the underdog winning was only 0.4% greater than favorites. The return shows the ratio of expected player win (negative indicates a loss) to money bet, assuming the player is laying 11 to win 10.

Underdog or Favorite Against the Spread

Side Wins Probability Return
Favorite 3,176 0.488165 -0.048375
Underdog 3,202 0.492161 -0.040746
Push 128 0.019674
Total 6,506 1.000000 -0.044560

Overs and Unders

The following table shows how often each game went over, under, and fell exactly on the over/under line. The return column shows the ratio of player win to money bet, assuming laying 11 to win 10. Not surprisingly, the table shows betting the under side to be the slightly better value, with a probability of winning 0.21% higher than over bets.

Under or Over Against the Total

Side Wins Probability Return
Over 3,232 0.492158 -0.051561
Under 3,246 0.494290 -0.047084
Push 89 0.013553
Total 6,567 1.000000 -0.044839

Money Line

The following table shows the expected return on money line bets, assuming one unit is bet per game. The return shows that betting road teams is the better value, with an expected return 0.53% higher.

Money Line by Side

Side Total Bet Total Return Expected Return
Home 6,567 6,288.75 -0.042371
Road 6,567 6,323.26 -0.037115
Total 13,134 12,612.01 -0.037115

The next table shows the expected return on money line bets, cut by whether the team is the underdog, favorite, or even. Surprisingly, to me at least, the table shows favorites to be the better value, with a return 0.46% higher.

Money Line by Favorite/Underdog

Side Total Bet Total Return Expected Return
Favorite 6,506 6262.13 -0.037483
Underdog 6,506 6232.14 -0.042093
Even 122 117.74 -0.034932
Total 13,134 12612.01 -0.039743

The next table shows the actual and estimated probability of winning by point spread. The estimated probability uses logistic regression to smooth out the ups and downs.

Probability of Winning by Point Spread

Spread Wins Games Actual
Probability
Estimated
Probability
Fair
Line
-15.5 26 24 0.923077 0.922718 -1194
-15 40 39 0.975000 0.916818 -1102
-14.5 44 38 0.863636 0.910510 -1017
-14 49 44 0.897959 0.903774 -939
-13.5 76 70 0.921053 0.896589 -867
-13 69 64 0.927536 0.888933 -800
-12.5 88 80 0.909091 0.880786 -739
-12 102 87 0.852941 0.872127 -682
-11.5 125 109 0.872000 0.862937 -630
-11 130 112 0.861538 0.853198 -581
-10.5 135 113 0.837037 0.842893 -537
-10 168 132 0.785714 0.832006 -495
-9.5 174 138 0.793103 0.820527 -457
-9 231 191 0.826840 0.808443 -422
-8.5 206 154 0.747573 0.795748 -390
-8 248 193 0.778226 0.782438 -360
-7.5 273 194 0.710623 0.768513 -332
-7 269 186 0.691450 0.753978 -306
-6.5 314 227 0.722930 0.738839 -283
-6 337 237 0.703264 0.723112 -261
-5.5 336 209 0.622024 0.706812 -241
-5 358 245 0.684358 0.689965 -223
-4.5 348 224 0.643678 0.672599 -205
-4 344 205 0.595930 0.654746 -190
-3.5 328 186 0.567073 0.636446 -175
-3 349 195 0.558739 0.617742 -162
-2.5 340 199 0.585294 0.598683 -149
-2 367 206 0.561308 0.579320 -138
-1.5 283 157 0.554770 0.559710 -127
-1 254 135 0.531496 0.539913 -117
1 254 119 0.468504 0.460087 117
1.5 283 126 0.445230 0.440290 127
2 367 161 0.438692 0.420680 138
2.5 340 141 0.414706 0.401317 149
3 349 154 0.441261 0.382258 162
3.5 328 142 0.432927 0.363554 175
4 344 139 0.404070 0.345254 190
4.5 347 124 0.357349 0.327401 205
5 358 113 0.315642 0.310035 223
5.5 336 127 0.377976 0.293188 241
6 337 100 0.296736 0.276888 261
6.5 314 87 0.277070 0.261161 283
7 269 83 0.308550 0.246022 306
7.5 273 79 0.289377 0.231487 332
8 248 55 0.221774 0.217562 360
8.5 206 52 0.252427 0.204252 390
9 231 40 0.173160 0.191557 422
9.5 174 36 0.206897 0.179473 457
10 168 36 0.214286 0.167994 495
10.5 135 22 0.162963 0.157107 537
11 130 18 0.138462 0.146802 581
11.5 125 16 0.128000 0.137063 630
12 102 15 0.147059 0.127873 682
12.5 88 8 0.090909 0.119214 739
13 69 5 0.072464 0.111067 800
13.5 76 6 0.078947 0.103411 867
14 49 5 0.102041 0.096226 939
14.5 44 6 0.136364 0.089490 1017
15 40 1 0.025000 0.083182 1102
15.5 26 2 0.076923 0.077282 1194

In the unlikely event you encounter a point spread with an absolute value greater than 15.5, then the probability of winning can be estimated as e^(-0.16*s)/(1+e^(-0.16*s)), where s is the point spread.

When I updated this page in 2018, there were a lot of obscure tables I was too lazy to update. However, I put too much effort into them at the time I made them to just throw them away. So, I split this off to Obscure Topics in Betting the NBA.


Written by: Michael Shackleford

Wizard Recommends