Count the gaps, not the coats
Take the defaults: 4,000 square feet, five coats, an applicator that lays a coat in an hour, thirty minutes of dry time between coats, three and a half hours to strip and rinse and dry the floor first, forty-five minutes of setting up and packing down, and an hour of waiting after the last coat before anyone walks on it.
That is 45 minutes plus 3h 30m plus five hours of coating plus two hours of dry gaps plus one hour of waiting: 12h 15m. The window is eight hours. The coating is five of those twelve hours; everything else is the floor being left alone.
What actually fits
Solve for how many coats fit in eight hours on the first night and the answer is two. Set up, strip, two coats with one gap between them and the final wait comes to 7h 45m, with fifteen minutes to spare. A third coat would need another 1h 30m and there is nowhere to put it.
The remaining three go down on a second night with no strip in front of them: 45 minutes of setup, three hours of coating, two dry gaps and the hour of waiting — 5h 45m, comfortably inside the window. So the closure has to cover two nights, not one, and that is the sentence the customer needs to hear before the job starts rather than at six in the morning on the day.
Splitting it is not free
Twelve and a quarter hours of work becomes thirteen and a half once it is split, because the second night pays for its own setup and its own final wait, and only one dry gap is absorbed by the break between nights. An hour and a quarter of extra labour is the price of the split, and it is a price worth naming when somebody asks why two nights costs more than one long one.
The gallons are the easy part
At 1,800 square feet a gallon, one coat on 4,000 square feet is 2.22 gallons. Five coats would be 11.1 gallons if every coat behaved the same, but the first one goes onto a bare stripped floor and drinks. At the 25 percent uplift in the form the first coat is 2.78 gallons and the total is 11.67 — call it 12, which is three four-gallon cases or two five-gallon containers plus a bit.
The stripper at 1,000 square feet per mixed gallon is four gallons of solution, which at one part to four parts water is 0.8 gallons of concentrate and 3.2 of water. The neutraliser at 1,500 square feet per gallon and 1:64 is 2.67 gallons of solution and about five and a quarter fluid ounces of concentrate — a figure small enough that it is worth measuring rather than pouring.
What the page refuses to decide
How many coats a floor should get, what dilution the stripper runs at, how long the finish needs between coats and when the floor is ready for traffic are not in here as figures of our own, and they are not derivable from arithmetic. They come from the product label, the safety data sheet and whoever wrote the specification, and the calculator takes them as inputs precisely because a wrong one changes the plan rather than the total. If the label dry time is forty-five minutes rather than thirty, the same five coats need three nights instead of two.
Questions people ask
How many coats of floor finish fit in an eight hour closure?
At the figures in the form, two on the first night — because the strip, the rinse, the setup and the final wait take 6h 15m of the eight hours before any finish goes down, and each coat then costs an hour to lay plus half an hour of dry time. On a second night with no strip in front of it, five coats would fit. The answer is driven by the fixed part of the night, not by the coats.
How much floor finish do I need for 4,000 square feet?
At 1,800 square feet per gallon, one coat is 2.22 gallons. Five coats is 11.1 if every coat is the same, but the first coat on a freshly stripped floor takes more; at a 25 percent uplift the total is 11.67 gallons. The uplift is a field rather than a constant because the honest source for it is your own gallon counts on the same kind of floor.
Why does splitting the job over two nights cost more hours?
Because setup, pack down and the wait after the last coat all happen again on the second night, while only one dry gap is saved by the break. In the defaults, 12h 15m of continuous work becomes 13h 30m across two nights — an hour and a quarter of extra labour, which is the number to quote when somebody asks why two shorter nights are not the same as one long one.
How much stripper concentrate does a 1:4 dilution need?
Four gallons of mixed solution at one part concentrate to four parts water is 0.8 gallons of concentrate and 3.2 of water, because one to four is five parts in total. If your label means one part in four parts total instead, it is one gallon of concentrate to three of water. Which reading applies is on the label, and the two are not interchangeable.
Is the floor safe to walk on after the cure time in the form?
That is not a question this page answers. The cure figure is an input you supply from the product label and from whatever the building requires, and the page only checks whether it fits in the window you gave it. A freshly finished floor is wet and slippery until it is not, and when that is depends on the product, the temperature and the air in the building rather than on any arithmetic here.