Updated October 2026
How This Painting Calculator Works
Nothing here is a black box. The calculator uses the same arithmetic you'd do on a clipboard, so you can check any number it gives you. For each room:
Walls = 2 × (length + width) × height − (doors × 20 ft²) − (windows × 15 ft²)
Ceiling = length × width
Trim = 2 × (length + width) × 1 ft
Paintable area = (checked surfaces) × coats
Then, across all rooms:
Gallons = total area ÷ coverage rate, rounded up
Paint cost = gallons × price per gallon
Labor = (total area ÷ labor pace) × labor rate
Bid = (paint + labor) × (1 + overhead/profit %)
A few things to know about those formulas:
- Coats multiply the area, not just the paint. A second coat costs you a second round of paint and labor. It's faster than the first coat in real life, but it isn't free.
- Trim is estimated as a 1-foot band around the room's perimeter, so 2 × (length + width) square feet. That's about right for standard baseboard plus casing. Use a bigger number for crown molding or wainscoting.
- The door and window deductions are standard sizes. A 3×7 door is 21 ft², and a typical 3×5 window is 15 ft². Sliders, bay windows, and double doors are bigger, so count an 8-foot slider as about two doors.
- Gallons are rounded up for the whole job, not per room. That matches how you'd actually buy paint when the rooms share a color. If every room is a different color, you'll buy more partial gallons than the calculator shows.
Choosing Your Settings
The defaults under Job Settings are starting points, not recommendations. The bid is only as good as these five numbers, so here's how to set each one.
Paint quality
The three tiers ($25, $40, and $65 per gallon) are rough contractor prices for economy, mid-grade, and premium interior paint. Your supplier pricing and contractor discount will differ, and prices change. If you always use the same product, the most accurate thing you can do is look up what you actually paid last month.
Coverage rate
Most paint cans claim 350–400 ft² per gallon. That number assumes a smooth, primed, non-porous surface. Real-world coverage is lower on:
- New drywall or bare plaster (it soaks up paint). Prime first, or plan on 250–300 ft²/gal.
- Textured walls and popcorn ceilings, where the actual surface area is bigger than length × width.
- Deep or bright colors, which often need an extra coat to hide.
Lowering coverage from 350 to 300 adds about 17% more paint. That's a cheap way to build in a waste factor.
Labor rate
This is what an hour of painting costs you: wages plus payroll taxes and workers' comp for an employee, or your own target pay grossed up for self-employment tax if you work solo. Business overhead goes in the overhead/profit field instead. If you're not sure where your rate should be, this breakdown of why trade bids come in too low walks through the math.
Labor pace
This is the setting most likely to make your bid wrong. The default of 150 ft²/hr is a rolling pace: one experienced painter rolling open wall. A real job also includes cutting in, masking, moving furniture, patching, and cleanup, and none of those produce square footage. Most painters who check their numbers against finished jobs land well below their rolling speed once everything is counted.
The best way to set it is from your own history. Take a recent job, add up every crew hour including setup and cleanup, and divide the paintable area (with coats) by those hours. That's your real pace. Use it here, and the calculator will price setup and prep time for you.
Overhead / profit
This percentage is added on top of paint and labor. It needs to cover everything that isn't the job itself: insurance, your truck, tools, phone, software, advertising, the hours you spend estimating jobs you don't win. Profit comes on top of that. See the note on markup vs. margin below before you pick a number.
Worked Example: Three-Room Interior Repaint
Here's a typical job: walls and trim in a living room and two bedrooms, two coats, standard paint, with every other setting left at its default.
| Room | Size | Doors / Windows | Area (1 coat) | Area (2 coats) |
|---|---|---|---|---|
| Living room | 16 × 14 × 9 ft | 2 / 3 | 515 ft² | 1,030 ft² |
| Primary bedroom | 14 × 12 × 8 ft | 2 / 2 | 398 ft² | 796 ft² |
| Bedroom 2 | 11 × 10 × 8 ft | 2 / 1 | 323 ft² | 646 ft² |
| Total | 1,236 ft² | 2,472 ft² |
Working through the living room walls: 2 × (16 + 14) × 9 = 540 ft², minus 40 for two doors and 45 for three windows, leaves 455 ft². Trim adds 2 × (16 + 14) = 60 ft², for 515 ft² per coat.
Here's how the bid comes out at the default 150 ft²/hr pace, and again at a more realistic 100 ft²/hr that includes cutting in, masking, and cleanup:
| Pace 150 ft²/hr | Pace 100 ft²/hr | |
|---|---|---|
| Paint (2,472 ÷ 350 → 8 gal × $40) | $320 | $320 |
| Labor hours | 16.5 hrs | 24.7 hrs |
| Labor at $45/hr | $742 | $1,112 |
| Subtotal | $1,062 | $1,432 |
| Overhead / profit (20%) | $212 | $286 |
| Bid | $1,274 | $1,719 |
The takeaway: changing one setting, the labor pace, moved the bid by $445, which is 35%. If your bids keep coming out lower than your gut says they should, check labor pace before anything else. A pace that only counts rolling time is the most common reason a painting estimate looks fine on paper and then loses money on the job.
What This Calculator Doesn't Include
It handles the core of a paint bid: area, paint, labor, and markup. It leaves out the things below, so add them yourself when they apply.
- Primer. New drywall, water stains, going from dark to light, or glossy surfaces all need a primer coat. The quick way to cover it is to price primer as an extra coat.
- Sundries. Tape, plastic, roller covers, caulk, patching compound, and sandpaper add up. Many painters add a flat amount per room or a percentage of paint cost. Either way, put a number on it.
- Drywall repair. More than a few nail pops means patching, sanding, and spot-priming, which is a separate line item.
- Hard access. Stairwells, vaulted ceilings, and anything that needs a plank or scaffold go far slower than the room average. Price them separately or lower the labor pace for those rooms.
- Doors, cabinets, and detailed trim. Painting door slabs, window sashes, or built-ins is brush work and slow. Many painters price it per piece instead of per square foot.
- Travel and minimum charges. A one-room job still costs a drive, setup, and cleanup. Set a job minimum so small jobs don't lose money.
Markup vs. Margin
The overhead/profit field is a markup: it's added on top of your costs. Margin is that same dollar amount as a percentage of the final price, and it's always a smaller number:
Margin = markup ÷ (1 + markup)
20% markup → 16.7% margin
25% markup → 20% margin
50% markup → 33% margin
This matters when you have a margin target. If you or your accountant says you need 20% margin to stay healthy, enter 25% here, not 20%. Mixing up the two quietly takes a few points off every job.
Frequently Asked Questions
How much paint do I need for a 12×12 room?
With 8-foot ceilings, one door, and one window, the walls come to about 349 ft². Two coats at 350 ft² per gallon is just under 2 gallons. Add the ceiling (144 ft² × 2 coats) and you need 3 gallons. Enter the room above to see the exact number for your settings.
Should I charge by the hour or by the square foot?
Most painters quote a fixed price that's built from square footage, which is what this calculator does. Customers like knowing the total up front, and you keep the upside when you work efficiently. Hourly billing makes more sense for repair work and small jobs where the scope can't be measured ahead of time.
Should I subtract doors and windows from the wall area?
For paint quantity, yes, and the calculator does it automatically. For labor, painting around a door or window takes cutting-in time, so many painters don't subtract openings when they estimate labor. If your rooms have a lot of openings, lower your labor pace a little to make up for it.
How many coats should I quote?
Quote two coats for most repaints. One coat works only when you're freshening up the same color over a sound, clean surface. New drywall needs primer plus two coats. Put the number of coats in the written estimate so the customer knows what they're paying for.
Why does my per-square-foot price look different from what other painters charge?
The per-square-foot number under the total is based on paintable area with every coat counted. Many quotes and online cost guides use floor area of the house instead, which is a much smaller number. Make sure you're comparing the same thing before you change your prices.
Is my estimate saved or sent anywhere?
No. The calculator runs entirely in your browser and nothing you type is sent to a server. Use Copy Estimate or Print / Save PDF to keep a copy. Refreshing the page clears it.