I am selling my 1918 home. I do not know what my amp service is. How do I figure it out looking at the breaker panel?

Should have a number on Main Fuses or Main Breaker, Maybe 60 Amps, 100 amps?

Do you have a circuit braker panel or ceramic fuses ? If circuit breakers, than your service has been updated since 1918 and should be mimimum 100 amp service. Get the part number (should be located on top switch in panel imbedded in plastic) then get online and get the amperage specifications from the panel manufacturer.

The size of your service is lowest rated item in the service.
The service conductors, meter pan, panel, all must be rated to a certain size. Typically they are all in sync, sometimes not.

A 100A service would need #2al, or #4cu, wire, and a 100A meter pan and a 100 or 125A rated panel.

In 99% of the cases, simply looking at the main breaker handle (if you have one) will tell you your service size.

Many old homes have split-buss panels with up to six "main" breakers. For these you need to look at the panel label.