Pensioners in Scotland share £9.58 billion in benefits, including the state pension, pension credits, disability benefit and other advantages.
This amounts to 8.7% of the UK total spend shared between 8.3% of the British population, providing £417 million more than a division based purely on population would, Mr Brown said.
The former chancellor has divided this total by the 1,020,190 state pensioners in Scotland and found the additional benefit amounts to £409 per pensioner.
He said: "When you include the Scottish share of pensioner benefits paid overseas, Scottish pensioners received a total of £9.58 billion in pensioner benefits. This represents 8.7% of total pensioner benefits across the UK, even though Scotland only has 8.3% of the UK population.
"The pensioner benefit spend in Scotland last year would have been £417 million less had it been based on Scotland's share of the UK population.
"So before the SNP start making plans for independence they have to find an extra £417 million that we currently receive from being part of the UK.
"I want us to do more and I am determined to fight for a better deal for OAPs including a 20-month freeze on energy prices under a new Labour government.
"But we should remember that under the last Labour government, 200,000 Scottish pensioners were taken out of poverty as pensioner poverty fell from 33% in 1997 to 11% in 2010.
"Before we throw all this away let us remember that the SNP have set up a review into the 'affordability' of pensions in an independent Scotland."
A spokesman for Scottish Finance Secretary John Swinney said: "As so often in the past, Gordon Brown has got his figures badly wrong. The reality is that, under Westminster, spending per head on the state pension is less in Scotland than in the UK as a whole.
"And this is the height of hypocrisy from Mr Brown given that the problems facing many private pension funds across the UK can be traced directly to his ill-judged £100 billion raid on private pensions when he was chancellor.
"State pensions are more affordable in Scotland than for the rest of the UK, and with independence we will guarantee it is triple-locked, meaning it will rise at least in line with inflation - and we will also review plans to increase the state retirement age to 67.
"Unfortunately, Gordon Brown is silent on Labour's backing for the Tories' plan to abolish savings credit for new pensioners, a move that will cost poorer pensioners more than £1,000 per year, as well as Labour's decision to means-test the winter fuel allowance."