PAINT PROJECT CALCULATOR
Painting.
Estimate finish paint and primer for named walls and ceilings, with editable coverage and one supplier-ready material list.
Supplier material list
Ready when you are.
Project totals include allowance. Matching materials are combined.
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Verify current product instructions, field coverage, color, sheen and package availability before ordering.
PAINT ESTIMATING GUIDE
How the Paint Project Calculator works
Build a coating takeoff from named areas and actual specifications. Finish and primer remain independent, and compatible quantities combine before purchasing containers are rounded.
Measure walls and ceilings
Total SF is the simplest starting point: enter measured surface area for one named section. For walls, enter the total linear feet of the faces being painted and their common height. A 40 LF wall at 9 feet is 360 SF on one face. The calculator never doubles wall length automatically. If both sides are in scope, measure both sides or create another section. For ceilings, length times width gives the horizontal surface area. Sloped ceilings need their actual surface measurements, not only the floor footprint. Use separate areas for different heights, colors or products.
Opening deductions and net paintable area
Add measured opening width, height and quantity. Their area is subtracted from the gross area for both finish and enabled primer. Deduct only unpainted portions; include painted door faces, returns and window trim separately when they are part of the scope. Deductions cannot exceed gross area. Small openings may be left in an estimating allowance if that is your documented practice, but do not deduct them and credit their area a second time.
Coats and editable coverage
Required gallons = net SF × coats ÷ coverage in SF per gallon × (1 + allowance / 100). Each area has independent finish paint and primer coverage. Finish starts with an editable 350 SF/gal baseline and two coats; primer starts with 300 SF/gal and one coat. These are estimating assumptions, not manufacturer claims. Enter the current product specification or a documented field rate before purchasing. The number is coverage for one coat. A lower rate increases gallons. Never infer a special coverage rate from a brand name, sheen, paint chemistry or application method alone.
Primer and finish paint serve different purposes
Enable primer only for the areas that require it and confirm the approved substrate and coating system. Primer has its own coats, coverage, paint type, method, manufacturer, product, tint, sheen and packages. A primer for porous drywall is not automatically suitable for metal, stains or a previously coated surface. Turning primer off removes its demand while preserving its settings for reopening or later use. Do not combine primer and finish as one purchase product, even when their color descriptions match.
Paint type, application method and spray loss
Water-based/Latex, Oil-based/Alkyd and Specialty/Other describe the specification. Roller, Brush, Spray and Mixed record the intended application. None of these choices silently changes coverage. Actual manufacturer data, specified film thickness, surface texture, porosity and field conditions control demand. Spraying may introduce transfer loss and overspray. Account for that in the entered effective coverage or in the selected material allowance. If the entered rate already includes the expected spray loss, do not add the same loss again as allowance. There is no universal spray or roller multiplier.
Manufacturer, product, color and sheen
Open Product specifications & available packages to record the manufacturer, complete product code, color name/code, sheen and data-sheet URL or reference. Record the basis for the entered coverage in the notes. A published coverage range is not a promise of field performance: use the applicable value for the specified film build, substrate and application. Check the current manufacturer technical data sheet and supplier availability. This calculator does not fetch or infer product coverage from a product name. Different colors and sheens remain separate purchases. Unspecified products remain separate by area until a complete matching specification is entered.
Manufacturer specification examples
BEHR PREMIUM PLUS Interior Eggshell Enamel lists 250 to 400 SF/gal. KILZ 2 All-Purpose Primer lists 300 to 400 SF/gal, depending on method and surface porosity. These are product-specific examples, not presets or universal rates. Verify the current data sheet and enter your applicable coverage above.
Quarts, gallons and five-gallon pails
Select the sizes actually available: one quart is 0.25 gallon, one gallon is 1 gallon, and a five-gallon pail is 5 gallons. Compatible raw requirements combine before rounding. The suggested purchase rounds demand up to the smallest selected package increment, then uses larger selected containers first to fill that volume. For 5.2 gallons with all sizes enabled, buy one five-gallon pail and one quart: 5.25 gallons. With gallons and pails only, buy one pail and one gallon: 6 gallons. Change the available package checkboxes to adjust the mix. No price data is used, so this is not a least-cost claim.
Material allowance and purchasing overage
Use the same 0%, 5%, 10%, 15%, 20% or Custom allowance control as Metal Framing. The default is 10%. Allowance is applied once to each section before compatible liquid demand is pooled. Container rounding may add more liquid beyond that demand; it is purchase overage, not another waste multiplier. Document whether your allowance covers handling, touch-ups, porous surfaces or application losses, and avoid overlapping adjustments in the coverage rate.
Worked example: walls with primer
A wall area measures 50 LF × 8 feet = 400 SF. Deduct one 3 × 7-foot door to get 379 SF. At two finish coats, 350 SF/gal and 10% allowance, demand is 379 × 2 ÷ 350 × 1.10 = 2.3822857 gallons. With quart and gallon sizes enabled, order two gallons and two quarts, totaling 2.5 gallons. One primer coat at 300 SF/gal requires 379 ÷ 300 × 1.10 = 1.3896667 gallons. Its separate purchase is one gallon and two quarts, totaling 1.5 gallons. These coverage values are example assumptions.
Worked example: compatible areas combine first
Two sections each require 0.4 gallon of the identical fully specified finish paint. With one-gallon packages, their combined 0.8 gallon needs one gallon, rather than independently rounding each section to a gallon. If the colors or sheens differ, keep two separate one-gallon purchases. Primer is always separate. Gallons are calculated without rounding intermediate section demand; displayed decimals are abbreviated for readability.
Common painting estimating mistakes
Avoid doubling wall faces without confirming scope, using floor SF as wall SF, forgetting extra coats, treating primer as finish, applying a universal rate to every paint, or counting spray loss twice. Do not round each compatible area before combining. Never assume every color is sold in every package size. Do not combine purchases just because the manufacturer matches. Material quantities exclude labor, surface repairs, masking, tools and access equipment.
Verify before purchasing
Confirm measured faces, ceiling slope, opening deductions, surface preparation, primer compatibility, required coats and specified film thickness. Check manufacturer coverage, tint and sheen, package sizes, batch consistency, spray assumptions and touch-up needs. Review Show the Math, copy the material list or print the PDF. Save the estimate to preserve its section settings and add it to a Project for the supplier material list. For a single fast calculation, use the separate Quick Paint Calculator.
Estimate responsibly. BidSimp is an estimating aid. Verify quantities, specifications, field conditions and project documents before ordering or performing work. Terms & Disclaimer