Exterior finishing calculators
Stains, sealers and anything that has to survive the weather.
Calculators in this category
1 calculator in exterior.
Interior finishes go onto surfaces someone built last week. Exterior finishes go onto whatever the last few winters left behind, and that changes the quantity far more than most people expect.
A manufacturer publishing 150 to 350 square feet per gallon is not hedging. The top of that range is new smooth timber; the bottom is a deck that has been out in the sun for six years and has opened up enough to absorb the first coat rather than hold it. Same tin, less than half the ground covered.
So the tools here ask what condition the surface is in, and they show which end of the published range they used. On a job where running short leaves a lap mark you cannot sand out, knowing which assumption produced the number matters more than a tidier answer.