I’d use a baseline plus adjustments rather than square footage alone. Start with the normal labor time for the size and scope, then adjust for the things that actually change production time — buildup, clutter, bathrooms, pets, kitchen condition, accessibility, and whether it’s a first-time/deep clean.
Photos or a quick walkthrough can help a lot with those adjustments. For a new property, I’d also treat the first estimate as having some uncertainty rather than trying to make it artificially precise.
The other piece is tracking estimated hours versus actual hours after the job. Over time that gives you much better numbers for similar properties and helps prevent a quote that looks reasonable but doesn’t actually cover labor, overhead, and your target margin.
