O.J. Simpson might have made more than $600,000 during his eight-plus years in prison.

After Simpson was granted parole on Thursday, that money is now his to spend and can’t be touched by the families of Nicole Brown Simpson and Ronald L. Goldman, who won a civil judgment against Simpson in February 1997 that, including interest, is now worth more than $40 million.

The reason the income is O.J.’s, unlike other money he might earn in the future, is because his NFL pension is protected by state law.

There has been much confusion as to how much Simpson was pulling in for his pension, but it’s fairly easy to calculate since the terms of NFL player pensions are public. One factor that adds to the confusion is the uncertainty of the age Simpson elected to begin collecting on his pension.

So let’s show you the math.

O.J. played in the NFL from 1969 to 1979.

NFL players who played before 1982 get a pension credit of $250 per season per month. Multiplying that by his 11 seasons, that’s $2,750 a month.

As part of a settlement in 2011, former players were given an extra payment of $124 per month per season in seasons played before 1975 and $108 per month per season in subsequent years. O.J. played six seasons before ($124 x 6 = $744) and five seasons after ($108 x 5 = $540) 1975. That’s another $1,284.

Adding $1,284 plus $2,750, that’s $4,034 a month.

That’s what O.J. would have made if he elected to start taking out his NFL pension at the age of 55. Getting paid that for 105 months in jail would mean O.J. made $423,570.

But if he waited until 65 — he just turned 70 — he would collect 2.619 times that, according to the formula. That would make his pension $10,565 a month.

Based on 57 months in jail after his 65th birthday, that’s $602,205.