How is Net Run Rate calculated?

A team's run rate (RR) is their total number of runs divided by overs faced. As an over is made up of six balls, each ball counts for 1/6 of an over for the purposes of calculating the net run rate, despite being normally written in cricket's notation as .1 of an over.

So if a team scores 250 runs off 50 overs then their runrate is . If they got that same score off 47.5 overs, their RR would be 

The concept of net run rate involves taking the opponents' final run rate away from the team's run rate. The only complication is that if a team is bowled out, it is not the balls faced which their score is divided by; instead the full quota of overs is used (e.g. 50 overs for a One Day International and 20 overs for a Twenty20 match).

Usually, runs and overs bowled are summed together throughout a season to compare teams in a league table, as the following formula shows-

Let's take as an example South Africa's net run-rate in the 1999 World Cup. South Africa's listing in the Group A points table published in the group stages was as follows:

                      P  W  L NR T Pts Net-RR    For        Aga 
South Africa          3  3  -  - -   6 +1.495  678/147.2  466/150 

The columns we are looking at here are the last three: "Net-RR", "For" and "Aga". The figure in the "Net-RR" column is achieved by subtracting the answer of the division in the "Aga" column from the answer to the division in the "For" column.

To use this example:

FOR

South Africa had scored, so far in the tournament:

• Against India, 254 runs (for 6 wkts) from 47.2 overs
• Against Sri Lanka, 199 runs (for 9 wkts) from 50 overs
• Against England, 225 runs (for 7 wkts) from 50 overs

Across the three games, South Africa scored 678 runs in a total of 147 overs and 2 balls (actually 147.333 overs), a rate of 678/147.333 or 4.602 rpo.

AGAINST

Teams opposing South Africa scored:

• India, 253 (for 5 wkts) from 50 overs.
• Sri Lanka, 110 all out from 35.2 overs.
• England, 103 all out from 41 overs.

In the case of Sri Lanka and England, because they were all out before their allotted 50 overs expired, the run rate is calculated as if they had scored their runs over the full 50 overs.

Therefore, the run-rate scored against South Africa across the first three games is calculated on the basis of 466 runs in a total of 50 + 50 + 50 = 150 overs, a rate of 466/150 or 3.107 rpo.

NET-RR

The net run-rate is, therefore,

  4.602  Run-rate for 
  3.107  Run-rate against 
  ===== 
+ 1.495  ANSWER 
  ===== 

Via :- Cricinfo, Wikipedia