How Old Should They Have Been?

We all know that census records can contain incorrect ages. When searching online databases, besides having the years of birth for people I am looking for, I have their approximate age in 1850, 1860, etc. This helps me eyeball if I might have the correct people or not. Having only the years of birth in front of me is helpful, but having the approximate at the time of the census saves me a little bit of time and reduces errors because I “subtracted” wrong in my head.