Paint calculator: gallons, coats & labor hours.
Work out net paintable area, gallons to order and painter-hours for walls and ceilings, with openings deducted, editable production rates and a live formula you can check.
- Feet or meters
- Spread rate from the data sheet or from volume solids & DFT
- Copy, print or save your results
1 · Surfaces Walls: perimeter × height
2 · Openings Deducted from walls
3 · Coating
Theoretical = 1,604 × volume solids ÷ DFT (mils). Zero-loss figure; keep a loss factor.
4 · Production & labor
Default rates: PaintsCalculator production-rate reference (one painter, one coat). Replace with your crew's tracked rates.
Cost
Area by surface
Save your results
Copy these results, then add your approved sample files in the trial brief.
Estimates only. Verify coverage against the product data sheet and production against your own crew records before you bid.
Standard formulas, shown on the page.
Nothing hidden. These are the same steps an estimator runs on a takeoff sheet.
1. Net paintable area
Walls = perimeter × height × quantity. Ceilings = length × width. Subtract openings (doors × area each + windows × area each) from walls only.
2. Paint quantity
Multiply area by coats, divide by spread rate, add a loss factor, then round up to whole containers (5-gal pails and 1-gal cans, or 10 L / 4 L / 1 L).
3. Theoretical spread rate
For coatings specified by dry film thickness, coverage at zero loss comes from volume solids. For example, a paint with 39% volume solids at 1.6 mils dry works out to about 391 sq ft/gal, inside the 350–400 range its data sheet lists.
4. Labor hours
Each pass is area ÷ production rate, per coat, with walls and ceilings at their own rates. Primer adds one pass. Prep is hours per 100 sq ft by prep level. Crew days divide by painters × productive hours.
Every default is labeled and editable.
Defaults give you a starting point. Your product data sheets and your crew's tracked rates should replace them.
| Input | Default | Basis |
|---|---|---|
| Spread rate | 350 sq ft/gal | Low end of the 350–400 sq ft/gal at 4 mils wet listed on Sherwin-Williams interior product data sheets and their paint calculator FAQ |
| Production rates | Walls 100 / 200 / 600, ceilings 80 / 180 / 600 sq ft/hr (brush / roller / spray) | PaintsCalculator production-rate reference, one painter, one coat. See also Servvian's interior estimating guide on tracking rates by task |
| Prep | 0.2 / 0.5 / 1.0 h per 100 sq ft | Light / medium / heavy prep, same reference |
| Loss factor | 5% | Standard interior paint allowance in Tallyard's waste-factor reference (10% for complex work). Editable assumption |
| Door / window area | 21 / 15 sq ft | 3 × 7 ft door, 3 × 5 ft window. Editable assumption |
| Primer spread, hours per day | 300 sq ft/gal, 7 h | Editable assumptions. Use your primer's data sheet and your crew's productive hours |
The math is easy. The areas are the work.
On a commercial set, the hours go into pulling wall, ceiling and finish areas off the drawings, matching them to the finish schedule, and redoing it when an addendum moves a partition.
- Surface areas from the drawings, each linked to the sheet and room it came from.
- Finish and coating schedules matched to the surfaces they apply to.
- Estimator review on every proposed area before it reaches your pricing sheet.
- Addenda go back through the same review, so you can reprice what changed.
Paint calculator questions.
How do you calculate how much paint you need?
Measure the paintable area (wall perimeter × height, ceiling length × width), subtract doors and windows, multiply by the number of coats, and divide by the spread rate on the product data sheet. Add a small loss allowance for touch-ups and application losses, then round up to whole containers.
How many square feet does a gallon of paint cover?
Many interior architectural paints list about 350–400 sq ft per gallon per coat at 4 mils wet film thickness on their product data sheets. Textured, porous or unprimed surfaces cover less. Always use the spread rate from the data sheet of the product you are bidding.
What is the formula for theoretical paint coverage?
For coatings specified by dry film thickness: theoretical coverage (sq ft/gal) = 1,604 × volume solids (as a decimal) ÷ DFT in mils. In metric: m²/L = volume solids % × 10 ÷ DFT in microns. This is the zero-loss figure; apply a loss factor for application method and surface.
What are typical painting production rates?
Published reference ranges for one painter, one coat, are roughly 100 sq ft/hr by brush, 200 sq ft/hr by roller and 600 sq ft/hr by airless spray on walls, with ceilings slower. Height, access, cut-in and prep change these numbers, so replace the defaults with your own crew's tracked rates.
Should I deduct doors and windows?
For quantity of paint, most estimators deduct openings from wall area. Many painting contractors still price labor on gross area because cutting in around openings takes time. This calculator deducts openings from paint and labor; adjust your rates if you price labor on gross area.
How many coats should I estimate?
Follow the specification. Repaints in a similar color are often one or two finish coats; new drywall usually gets a primer plus two finish coats; color changes and deep colors may need more.
Can this calculator estimate a whole commercial job?
It is built for quick checks and room-by-room or area-by-area estimates. On a full commercial set, the slow part is getting accurate wall, ceiling and finish areas off the drawings. That is where RenderDraw's AI takeoff with estimator review helps.
Stop measuring walls by hand on bid week.
Send one painting or coatings plan set. See the surface areas RenderDraw extracts, with sources, and what it flags for your review.
- Upload the plans, finish schedule and specs (plus an addendum if you have one).
- RenderDraw reviews the set and the scope you want tested.
- We follow up with the extracted areas, flagged items and next steps.