Cost per square foot is a comparison unit, not a costing method. It is produced at the end of the arithmetic, by dividing what a job costs by the area it covers, and it is genuinely useful for checking a bid against the market and against your own history. Used as an input, by taking somebody else's figure and multiplying, it produces a price that has no relationship to what your crew costs or how fast they work.
Working it out from your own jobs
Take a building you clean. Record the hours actually spent, across several visits so an unusual week does not dominate. Multiply by your loaded hourly cost, which is the wage with employer payroll tax and insurance on top. Add supplies and equipment per visit. Divide by cleanable square feet. That is your cost per square foot for that space type at that frequency, and it is worth writing down against the building so next year's review starts from a fact.
Why the figure moves so much between buildings
Space mix is the dominant variable: restrooms cost several times what open office does per square foot, so two buildings of identical size can differ substantially. Frequency is next, because fixed time per visit spreads further on a daily contract. Then access, floor type and how much the occupants leave behind. A single blended figure across a mixed book is an average of things that are not alike.
Carpet cleaning is priced on a different basis
Carpet extraction is priced per square foot or per room, but the cost driver is machine time and drying rather than labour hours in the ordinary sense, and the setup time does not shrink with the job, which is why a minimum charge sits under every carpet quote. Commercial carpet rates should carry that minimum explicitly, or a small job in a large building will be priced below the cost of arriving.
Questions people ask about cleaning cost per square foot
How do I convert an hourly rate to a rate per square foot?
Divide your loaded hourly cost by your production rate for that space type in square feet per hour. That gives cost per square foot; apply your margin to reach a price.
Is per square foot the right way to quote?
It is the right way to compare. Quote a monthly figure and show the rate underneath it so the buyer can check the comparison themselves.
Why is restroom cleaning so much more per square foot?
Fixtures, restocking and the standard expected. It is the area where a low production rate is correct rather than a sign of a slow crew.