Primer Calculator
Estimate primer gallons, quarts, and cost by surface type
Total surface area to be primed
Substrate affects primer coverage rate
Quarts
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quarts
Primer Gallons
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gallons
Estimated Cost
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USD
Disclaimer: Results are estimates based on standard formulas. Not a substitute for professional advice from a licensed contractor, engineer, or architect. Verify all calculations before making purchasing or construction decisions.
How to Use This Calculator
Priming is the foundation of a durable paint job. Matching the primer coverage to your substrate prevents bare spots and costly rework.
- Measure the total wall area in square feet
- Select the surface type (Drywall, Bare Wood, or Patched)
- Enter dimensions in the calculator
- Buy an extra quart for touch-ups and hard-to-reach corners
Expert Insights
Smart analysis for your Painting project
Substrate Coverage Tuning
Bare wood drinks primer at 200 sq ft/gal, while sealed drywall reaches 300 sq ft/gal. AI adjusts coverage based on your selected surface.
Quart Right-Sizing
For small remainders, a quart covers ~100 sq ft and avoids overbuying full gallons. The calculator splits gallons and quarts automatically.
Cost Benchmarks
Quality primer runs $20-$30 per gallon. Budget an extra 10% for second coats on porous or heavily patched surfaces.
Calculation Formula
Coverage = Drywall 300 | Bare Wood 200 | Patched 250 (sq ft/gal)
Gallons = ceil(Wall Area / Coverage x 10) / 10
Quarts = ceil((Wall Area mod Coverage) / 100)
Cost = ceil(Gallons x $25)
Primer Type Comparison
| Primer Type | Best For | Coverage (sq ft/gal) | Cost per Gallon | Coats Needed |
|---|---|---|---|---|
| Latex Primer | Drywall, patched walls | 300 | $20-$30 | 1 |
| Oil-Based Primer | Bare wood, stains | 200 | $25-$40 | 1-2 |
| Shellac Primer | Knots, smoke, water stains | 250 | $30-$50 | 1 |
| Bonding Primer | Glossy, tile, laminate | 250 | $35-$55 | 1 |
Authority References
Our calculations are based on guidelines and standards from these authoritative sources:
- Master Painters Institute (MPI) — Surface Preparation & Priming Standards. Learn more
- Painting and Decorating Contractors of America (PDCA) — Cost Estimating Standards. Learn more
- SSPC: The Society for Protective Coatings — Surface Prep & Primer Application. Learn more
Frequently Asked Questions
How much area does a gallon of primer cover?
A gallon of primer covers about 300 sq ft on drywall, 250 sq ft on patched surfaces, and 200 sq ft on bare wood, which is more porous.
Do I need primer on already-painted walls?
If the existing paint is in good condition and the new color is similar, you can skip primer. Use primer on bare drywall, bare wood, patched areas, or when covering a dark color.
How much does primer cost?
Primer averages $20-$30 per gallon. A typical 400 sq ft room needs 1-2 gallons, costing roughly $25-$50 for materials.