For me it varies a lot, I think it's very easy to think you are working when you are not. But also easy to work and not realise it.

I think a lot about Joel Spolsky's post [1] on the subject. It depends on what you are doing but I think in software development you need to look at effectiveness rather than time spent.

[1] https://www.joelonsoftware.com/2002/01/06/fire-and-motion/