The last thing you’d want on any type of window coverings is for it to look too small, in length, width, hung too low, etc. those extra inches add to the cost but are always going to be worth it in how it ultimately looks

Thanks. I don't mind the cost. But I got a quote from a local place that measures and installs for you ans she said they only add about 1 to 1. 5 inches and never up to 6. So just wanted to check in on that.

Sorry 1.5" on all the sides or total? I don't like wood blinds but IMO if you must then make sure they do the job you want , so if that is blackout then IMO go the 3" all around . If you don't care if light seeps through on the sides go thinner.

Thanks. We have about 3 inch trim around the window. It thought that might help with light.

I don’t think there’s any kind of hard and fast rule, maybe the website accounts for mismeasuring, sun direction, region, so their blinds will work for anyone anywhere whereas the local person is a little more specific. I’d tape up some paper over the window with 3 inch extra and a piece with one inch extra and just see if you happen to like one more than the other.