How do I figure Roth IRA withdrawals after converting multiple times?

IRS Publication 590b says

Order the distributions as follows.

1. Regular contributions.

2. Conversion and rollover contributions, on a first-in, first-out basis (generally, total conversions and rollovers from the earliest year first). See Aggregation (grouping and adding) rules, later. Take these conversion and rollover contributions into account as follows:

   a. Taxable portion (the amount required to be included in gross income because of the conversion or rollover) first, and then the

   b. Nontaxable portion.

3. Earnings on contributions.

Disregard rollover contributions from other Roth IRAs for this purpose.

There is a lot more detail in Pub 590b about what is taxable, what is subject to penalty etc. but this is enough to start with.

As a general rule. it is not advisable to take premature distributions from a Roth IRA unless one really really needs to do so and there is no feasible alternative....

It seems that my situation is greatly simplified by two facts — the Roth has only converted assets and no contributions, and I’m old enough (past 59 1/2) that all withdrawals after the account has been open 5 years will be “qualified” and not taxable.

It seems that even if I convert over multiple years, everything can come out tax-free after 5 years from the start of the year of the first conversion. Of course, any converted assets (upon which taxes were paid as a result of the conversion) will not have had as long to grow.