For human-ish blob (edit: on a parachute) weighing 100 kg dropping from 20 km, I got around 14 minutes under the simple equation of motion, with drag proportional to speed squared. It'd probably be closer to 10 minutes for stratified atmosphere, but I can't be arsed to calculate it that precisely. :PDude how long do you think it takes to ride an ejected pilot's chair with parachute down from 70k+ feet? That's gotta be like something around 30 minutes.
Did you use the cross-sectional area of a parachute, or a person? How'd your foot heal up, btw?? Been too long, good to see ya around :).
Cross-section of parachute, yes, sorry for confusing wording earlier. It mostly corresponds to 1.7-2.0 air resistance coefficient in all those plug-n-play calculators on the internet if you want to cut corners. Foot's OK. What's puzzling is that I can jump rope and do dexterity ladders like it's nobody's business, but running gives me pins and needles progressing to stabbing pain. So kinda not doing that.