Abbott has been in Parliament for 21 years. The rules stipulate the base of his pension is 6.25 per cent of the base parliamentary salary of $195,130 multiplied by the number of years of service.

Tony Abbott faced a leadership showdown at Parliament House on Monday night. Credit:Andrew Meares

For Abbott, that's 21 years, which works out at $256,000. But he won't get that much. The base of the pension is limited to 75 per cent of the parliamentary base salary, which means he'll be limited to $146,350.

On top of the base he will get extra for the time he has been a minister, the opposition leader, and the prime minister.

The extra works out at 6.25 per cent of the extra salary for each job, multiplied by the number of years he has been getting it. He was a minister for nine years, the opposition leader for four years, and the prime minister for two years. The loadings are 141,469, 165,861, and 312,208.