Primer calculator
Area, coverage, coats and can size: you get the primer or sealer needed to prep the surface before painting.
Purchase quantity
1.453 gal
Net measurement: 1.321 gal · Waste 10 %
- Primer or sealer2 bucket
- Area to paint645.835 ft²
- Litres with waste1.453 gal
Your prices per language/currency. Used when you enable “Use my prices” in calculators. My prices →
How it's calculated (visible formula)
primer = area ÷ coverage × coats; cans = ceil(primer × (1 + waste) ÷ can size)
- Net geometric measurement, no waste.
- Adjustable waste % for cuts and breakage.
- Purchase rounded up to sellable units (boxes, bags, buckets, boards).
How to calculate it, step by step
- Measure the area needing primer.
- Choose a product for the surface (drywall, wood, metal).
- Check coverage per coat.
- Work out gallons (usually one coat).
- Round up to cans.
Worked example: 645 sq ft of new drywall, 300 sq ft/gal, 1 coat
- 645 ÷ 300 ≈ 2.15 gal
- +10% ≈ 2.4 gal
→ Three 1-gallon cans (or 1 five-gallon).
Common mistakes
- Skipping primer on new drywall — paint flashes.
- Water-based primer over oil paint without prep.
- Thinning more than the label allows.
Pro tips
- On new drywall, primer evens out paper and compound.
- Over smoke or water stains, use a stain-blocking primer.
- Respect drying time before topcoating.
- Tint primer toward the final color for better hide.
From calculation to quote
Add labor, overhead and your margin, and generate the professional PDF.
FAQs
- Do I need primer on new drywall?
- Yes — it evens out absorption between paper and compound.
- Primer or paint-and-primer?
- Use a real primer on bare drywall, stains or big color changes.
- How much does primer cover?
- About 200–400 sq ft per gallon.
- Can I paint without primer?
- Over sound paint of the same type, yes; on new or porous surfaces, no.
- What primer for metal?
- A rust-inhibiting or bonding primer.
- Primer or sealer?
- Sealer consolidates chalky surfaces; primer improves adhesion.
Sources and standards
Maintained by Srikanta M · Formula v1.0.0 · Verified 2026-09-10 · Updated 2026-09-10 · Limits: quantity estimation, not structural design or site supervision.