If you have more than one IRA, it is my understanding you lump them all together to come up with your total but you only have to take your the distribution from one IRA account.

Correct. IRA's must be combined to determine the amount of the required minimum distribution but any or all of the IRAs can be the source of the distribution at your discretion.

IRS Publication 590 has all the details

I would reword that just a little differently Demosthenes ...
For instance, RMDs for IRAs ( traditional, SEP and SIMPLE IRAs) must be calculated separately for each IRA, but the total of the RMDs for all the IRAs ( owed by the individual- i.e does not include inherited IRAs) may be distributed from one of his/her traditional IRAs .


Technically, combining all the year-end FMV could give the same results as calculating them separately, but that would be true only if all the IRAs had (a) a non-spouse beneficiary or a spouse beneficiary who is not more than 10 years younger than the IRA owner or (b) a spouse beneficiary who is more than 10-years younger than the IRA owner.

Safest bet? Follow the guidelines and run the calculations separately