How do you estimate cleaning time before sending a quote?

I’m curious how cleaning business owners estimate labor time before sending a quote, especially for a new property.

Square footage and number of rooms are easy to get, but things like buildup, clutter, pets, bathrooms, and the overall condition can change the actual cleaning time quite a bit.

Do you usually estimate from experience, use a formula, ask for photos/videos, or visit the property first?

And how often does the actual cleaning time end up being very different from what you originally estimated?