I have been thinking and I kinda don't know as it is so variable. If my b/f is with me in the am, it may be about 10 min. or less, as he has an am erection, a condom ready and a little lube & vibe for me; I am ready.
More satisfying penetration sex is thankfully much longer but duration? I don't know as we frequently change positions, which is like foreplay for us but so much more! I always try to have an orgasm prior to penetration(except in the am) so whatever happens then, is a bonus!
I guess I would figure foreplay as all part of intercourse and say 45 plus min for us. Sometimes so much longer, thankfully.