How do I estimate Ohio capital gains for selling my home I have lived in for over 60 years?

Ohio will not tax that. If you qualify for the Federal home sale exclusion* (and you probably do), the capital gain is also excluded from the Ohio state return.  

*The capital gain on the sale of your primary home is not taxable (up to $250K, $500K married). To be eligible you must have lived in and owned the home for at least 2 out of the 5 year prior to sale. You do not even need to report it on your tax return, unless you got a tax document, usually a 1099-S. The 1099-S may have been included in your closing documents, instead of arriving in the mail, in Jan. or Feb. of the following year.

https://www.irs.gov/taxtopics/tc701