Do you actually need a tent footprint?

The two jobs a footprint does

The first is abrasion. Grit, pine duff and gravel work at a thin floor every time you move, and the wear shows up as pinholes long before it shows up as a tear.

The second is hydrostatic. Your hip and shoulder press down on a wet floor with a lot of pressure per square inch, and a 1,200 mm floor will let water through under that load even though the same fabric shrugs off rain. That is the failure people describe as the tent 'going porous' after a wet night.

A footprint does neither of the jobs people often hope for: it does not make the tent warmer, and it does not reduce condensation.

The maker's footprint versus a sheet of plastic

Branded footprints run five to seven ounces and $60 to $70, and they are cut to the tent so they clip in and support a fly-only pitch. That last part is the real argument for buying one.

Polycryo window-insulation film weighs one to two ounces, costs a few dollars a sheet, and protects just as well against grit. It is the single most common substitution people make, and it works. Tyvek is the middle option: tougher, noisier, about three ounces.

Cut it smaller than the floor

Whatever you use, trim it an inch or two inside the tent's footprint on every side. A groundsheet that sticks out past the fly catches rain and channels it directly under the tent, which is worse than having no groundsheet at all.