Calculating RMD for someone who is younger than 73?

Have a weird situation where a client has to mimic an RMD for a retirement account so that their account doesn't affect their wife qualifying for medicaid (in-home care, she has dementia). Since he's early 60s the 10% penalty won't apply. But I need to calculate how much his RMD would be.

What IRS table would I use to calculate this? Let's say he's 61. It's just a regular old IRA. Not inherited.

Thanks a lot.