Depends also on the area of glass. I have to almost completely shed my south facing normal size windows on sunny warm days.

You may be ought to try a computer model, this will tell you everything.

Whole house building physics model, it will give you heat demand and identify how many days a year that you will be uncomfortably hot. It models solar gain, against weather and sunshine.

Beware of west facing glazing, this can be bad for increasing overheating in the enemies when the sun is low and house warm already.

I don't have any guidance but I am interested in the question, as I'm trying to work out the answer for my own house. Brise soleil supplier websites have some formulae, but fascinatingly they aren't the same formulae. The height of the overhang above the glass also affects how it works, as well as the width. Draw rays of the sun at midwinter and midsummer to see why.

I'm lucky that I have windows facing due south but even so I've postponed doing much more calculation or design for a while and will wait and see how the temperature develops over the spring and summer. It was up to 23°C during March but we're back down to 22°C now. We're contemplating using one or two patio parasols as shading if we just need a bit.

As Tony says, a west facing aspect is more difficult because the sun is lower in the sky and an overhead projection doesn't help so much. Some people use vertical shading at the side of the window, or otherwise movable shading of some kind.