Batting average:
why not-outs change the denominator

The number that sums up a batter

A batting average answers a simple question: how many runs does this batter score for each time they get out? A figure of 45 means that, on average, a batter makes 45 runs before being dismissed. It is the main measure of consistency in cricket scorecards, from club level to Tests.

It looks like an ordinary average, but there is a twist that surprises newcomers. Innings that end with the batter not out are not counted in the divisor. The reasoning is that a batter who finishes unbeaten has not yet failed, so the innings should not be treated as one.

This one rule explains most arguments about averages. A middle-order player who bats at the end of innings, or in chases, gets more not-outs, and their average gets a lift for it.

The average also tells you something about how a batter's innings are distributed. A batter with an average of 45 may have made a series of scores between 35 and 55, or they may have made a handful of centuries and many single-figure scores. The mean cannot distinguish the two patterns, and the median score, or the proportion of scores above 30, is a useful companion.

Formula and worked example

Averages are normally given to two decimal places, so a batter with 8,000 runs from 150 innings with 20 not-outs has 8,000 ÷ 130 = 61.54. Divide by 150 instead and you would get 53.33, which is the wrong measure.

How not-outs change the answer

Take a batter who has 12 innings, 450 runs and 2 not-outs. Dividing by innings gives 37.5, but only 10 of those innings ended in a dismissal. The correct average is 450 ÷ 10 = 45.00.

The table shows how sensitive the figure is. With the same 450 runs, five not-outs turn a 37.50 average into 64.29. That is also why a small sample of innings can produce a startling average, and why selectors look at a longer run of games.

Match context completes the picture. An unbeaten 40 that wins a tight chase is worth more to the team than a dismissal on 55 in a lost cause, yet the average treats the first as a plain 40 with no dismissal and the second as 55 with one. The average is a tally of runs and wickets, and it was never designed to weigh the importance of an innings.

Raising or lowering the average

Because the denominator moves only when a batter is dismissed, a not-out knock raises the average for free, while a dismissal is double-edged: it adds runs to the numerator and one to the denominator.

1. 1Start with 450 runs and 10 dismissals: average 45.00.
2. 2A not-out 30 makes it 480 ÷ 10 = 48.00.
3. 3Instead a dismissal for 30 makes it 480 ÷ 11 = 43.64.
4. 4To reach exactly 50.00 after one more dismissal needs 50 × 11 = 550 runs in total, so 100 runs in that innings.

The last line is what commentators mean when they say a batter needs a hundred to get to an average of 50. It is the easiest way to see the number as a target rather than a mystery.

Reading a career average sensibly

Averages are not comparable across eras or conditions without caution. Pitches, rules, bowling attacks and even the ball change what a score of 40 means. A 40 on a difficult pitch against a strong attack can be worth more than a 55 on a flat track against weaker opponents.

Role matters too. An opener faces the new ball, and a lower-order player may only bat in short bursts. The same average from those two positions tells you different things. When comparing, look at innings count, the format, and the spread of scores as well as the headline.

Combining averages across formats or seasons

A common slip is to average two averages. Say a player scored 3,000 runs with 60 dismissals in one format, an average of 50.00, and 2,000 runs with 50 dismissals in another, an average of 40.00. The simple mean of 50 and 40 is 45.00, but the combined average is different.

The combined figure leans towards the average with more dismissals behind it. The same method is used to merge seasons, teams or competitions, and it is also how a career figure is produced from year-by-year lines.

Keep format labels attached whenever you quote an average. A figure of 38 in a first-class competition is not directly comparable to 38 in one-day matches, because the number of overs, field restrictions and the strategy of the innings are different, and so are the opposition and the pitch.

Common mistakes

• Dividing runs by innings played instead of dismissals.
• Counting retired hurt as a dismissal. Under standard scoring it is a not-out.
• Mixing formats. Test, one-day and T20 averages are kept separately for a reason.
• Using a short sample. Four innings can give an average of 120 or 8.
• Treating the average as the only measure. Pair it with strike rate and the number of innings.

An online calculator is a handy way to check the arithmetic quickly, but the rule underneath is always the same: runs on top, dismissals below.