Over/Under Betting: Everything You Need To Know

Our natural human state is to be point or goal positive; even when that conflicts with statistical analysis. 

Take this NFL line for example:

Chiefs vs Ravens 47.5 – Over (-200), Under (+110) 

Both of these teams are strong on offense, so automatically we might assume that there will be lots of points. But have we considered all of the key variables:

• Defensive quality
• Player availability
• Player fatigue

Weather conditions – Cold, heavy rain, strong wind

Red zone inefficiencies on the day

Is 48+ points between the Chiefs and the Ravens viable on this particular day? Sometimes, the contrarian ‘unders’ position is actually the +EV play, despite the general game models of the two teams.

We’ll call this situational variance, which is one of the key drivers of the over/under market. In this guide, we’ll examine some others – such as pace of play and team efficiencies, as well as taking the view of sports betting sites: how are lines set? 

How Over/Under Betting Works in US Sports

The top NFL betting platforms set their totals lines following comprehensive statistical analysis of the two teams involved.

Additional line movements are made after further contextual analysis closer to kick off: 

• Will the weather be a factor? 
• Are there notable roster changes? 
• What is the motivation level of each team? 

For bettors, the task is to translate these odds into implied probabilities, which provides a view on whether it’s the overs or unders side – or perhaps neither – that represents value.

An example would be an NBA contest between two offensively sound teams, with a line of 225.5 provided by the sportsbooks. You have projected a final result in the region of 231 points, so the overs bet appeals.

How Total Over/Under Betting Works

To remove the tie and make over/under betting a two-way market, sportsbooks offer a line with a .5 at the end.

For example, the line between the Cavaliers and the Warriors could be around 227.5. You now have one of two bet choices to make:

• Over – 228 or more points will be scored
• Under – 227 points or fewer will be scored

To determine the outcome, the points tallies of the Cavs and the Warriors are added together to create an overall total – bets are settled according to this number.

Best US Sports for Over/Under Betting

For newcomers to over/under betting, the MLB can be a good starting point. You can build your projections around the starting pitcher, creating medium variance opportunities.

The NFL can be more volatile, with weather sensitivity a key factor, but the NHL is interesting as hockey is an inherently low-scoring sport. In theory, that lends itself to over/under betting… although outcome randomness can be a factor.

The leading NBA betting sites offer over/under lines too. The sheer breadth of scores that can be posted in NBA games presents both an opportunity and a source of variance to bettors.

Understanding Pace, Efficiency, and Totals

Pace and team/player efficiency are two of the key variables that drive over/under markets.
In the NBA, some games are fast-paced and lend themselves to end-to-end, high scoring action; this could add as many as 8-12 points to projections.

In the NFL, snap rates can impact the nature of possession plays, while in the NHL both shot volume and quality are determinant factors.

Even in the MLB, changes in pitcher or pitching style can impact the over/under lines.

Drivers of Value in Totals Over Under Betting

A quick checklist of factors that shape value in over/under betting:

• Pace mismatches
• Offensive/defensive balance – injuries/absentees 
• Weather conditions – NFL, primarily
• Rotated starters
• Pitcher/batter matchups

Imagine two NFL teams strong on offense but weak on defense. The sportsbooks will set a high totals line – hoping to ‘trap’ bettors hellbent on backing the overs side.
This can present a value opportunity on the unders side; especially if weather conditions or player unavailability can lend a hand.

Case Study — Total Over/Under Betting Scenario

The Chiefs are taking on the Ravens, and the sportsbooks have set the total points line at 49.5.
Your projections suggest this line is about right, but you notice that strong winds and fierce rainstorms are heading to Baltimore. This could impact quarterback efficiency, as well as the ability of wide receivers to catch the ball.

What was initially a marginal market now has strong ‘under’ signals, which is an example of how expectations and actual outcomes can change quite quickly – especially on gameday.