Underlayment Calculator
How much underlayment do you need? Enter your room size and roll coverage.
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Room area—
Estimated cost—
Shop floor underlayment →
How this calculator works
It finds your room area, adds 5% for overlap and trimming, then divides by the square footage each roll of underlayment covers.
Worked example — a 12 ft × 10 ft room, 100 sq ft per roll:
120 sq ft × 1.05 = 126 ÷ 100 = 2 rolls.
Match it to your floor
Laminate, vinyl and hardwood each call for a specific underlayment. Some click floors come with padding pre-attached — check before buying separate rolls.
Frequently asked questions
How much underlayment do I need?
About the same as your floor area plus a small overlap allowance — divide by the roll’s coverage.
Do I need underlayment under vinyl plank?
Only if the planks don’t already have an attached pad — and never double up.
Planning a flooring or tile project
Buy the material for one room from the same product batch when possible. Layout, pattern direction, damaged pieces, and cuts around doors or cabinets affect waste, so a simple rectangular calculation is a starting point rather than a cutting plan.
How to use this estimate
- Measure the project in the units shown and recheck your measurements before ordering.
- Use the waste allowance as a planning buffer, not as a substitute for a detailed material takeoff.
- Compare the result with the package yield, coverage, or weight listed by your supplier.
- Prices are user-entered estimates and may change by location, product, delivery, and season.
Accuracy and limitations
Calculapedia provides educational planning estimates. It does not inspect your site, select products, guarantee quantities, or replace a contractor, engineer, architect, building official, or supplier. Confirm the final quantity and any safety or code requirements before buying or building.