Per square foot or per line item

A price per square foot works when the jobs being priced have similar preparation, access and scope. When those conditions differ, calculate the actual tasks and costs as line items first. You can then divide the resulting selling price by area without hiding the work behind an average.

Two 1,800-square-foot paint jobs, $2,200 apart in cost

Every number below is invented so the arithmetic is easy to follow. Your burdened rate and your production will be different; the shape is the point.

Both jobs are 1,800 square feet of paintable wall surface. Your interior number is $2.10 per square foot and your burdened labor cost is $48 per person-hour, so both estimates come out at $3,780. Say which surface you measured: "per square foot" means wall area to some painters and floor area to others, and there is no fixed conversion between wall area and floor area.

Job A is a new-construction great room and hallway: 10-foot ceilings, primed drywall, empty house, one color, ground floor. Two painters, a day and a half each.

Job B is an older bungalow: six rooms, 22 inside and outside corners, 14 windows, nine doors, plaster to patch, three colors, occupied, half of it upstairs. Two painters, four days each.

The whole 40-hour gap traces back to conditions already listed in Job B's description. Job B is Job A plus those conditions:

Forty hours at $48 is $1,920. Add the assumed extra travel, loading and unloading ($144) and the extra compound, primer and third color ($180), and you have the $2,244.

Same unit, same quantity. Job A subsidizes Job B, and you find out at year end — if your job costing is good enough to tell you.

The five conditions that break a unit price

Setup does not scale. Drive, unload, cover, mask, mix, clean up, reload. That block runs roughly the same whether you cover 200 square feet or 2,000, and on a small job it can eat half the day. Time it on ten jobs and you will have your own number. A four-square roof repair — 400 square feet, since a roofing square is 100 — still needs disposal arranged, a delivery staged and a permit if your jurisdiction requires one. Many do not; your building department sets that line.

Cut-up space costs more per foot. One great room and six bedrooms can have the same area with very different edge counts. Flooring layouts also change cut waste: use the chosen manufacturer's instructions and a layout plan rather than a fixed waste percentage for every room.

Height and access. Second stories, narrow stairwells, no driveway to stage from, a condo elevator you have to book. Roofing prices this openly: steeper pitches and second-story work carry their own adders, because production drops and fall protection changes the setup.

Prep varies more than the finish. A pour over prepared subgrade and one where you first break out a failed slab are the same square footage. So are primed drywall and plaster with 30 cracks. The finish is predictable; the prep is where the hours disappear.

Obstacles the tape measure never sees. Furniture to move, tenants in place, pets, one working bathroom, restricted delivery windows, a dumpster with nowhere to sit.

None of this is a painting problem. A roofing square hides pitch, tear-off layers and decking repair. A linear foot of gutter hides corners and terrain. A per-room cleaning price hides room size and condition.

Test your unit price against your last ten jobs

Take ten finished jobs of the same type and divide each one's total cost by its units. That gives the unit cost, not a selling price: overhead and the profit you need still have to be recovered consistently.

There is no industry threshold for how tight that spread should be, so do not trust one that sounds official. Look at the shape. If the ten numbers cluster, the unit price is doing real work. If your worst job needed roughly double what your best did, you are averaging and the easy jobs are carrying it. Narrow the unit to a job type that behaves consistently, or stop leading with it.

Price by line item, present by the unit

Build the estimate internally as line items — labor hours by task, materials by quantity, mobilization, disposal, then overhead and profit. Present it in whatever form the customer can compare: one number, a unit price, or the line items if they are bidding it out. It stays honest as long as the unit price falls out of this job's takeoff, not out of memory.

Where the unit price stops being honest

Three things hide what the customer should know: an undefined unit — "per square" that may or may not include tear-off, disposal and decking repair; prep excluded but the exclusion never written down; and a quantity called approximate with nothing saying what happens if the field measurement differs. That last one belongs in the estimate as a change order term, agreed before you start, not discovered on the invoice.

Written scope also matters for contract compliance. California CSLB guidance requires a written home improvement contract over $500 and signed written changes before changed work starts. Check the requirements that cover your own project. As a practical approval process, describe additional work, its price and schedule impact in writing before proceeding.

Building the estimate this way in DoneQuote

DoneQuote drafts quotes with line items priced from your service catalog. Write the unit, quantity, included preparation and exclusions on the quote, then review the draft and customer view before sending. Do not treat the quote as a private job-cost sheet: the quoted scope and selling prices are customer-facing.

Summary

• A unit price is an average; averages fail on small, cut-up, high-access and heavy-prep jobs
• Run your last ten jobs through it; a wide spread means you are averaging
• Build by line item, present by whatever the customer can compare
• Write down the quantity, the inclusions, the exclusions and what happens if the measurement changes — then check what your state requires

The number itself is not the problem. Quoting it before you have seen the job is.