Metric example
Input Area 120 m², roughness factor 1.15, waste rate 10%, primer 10 m²/L ×1 coat, 16 L can, 98 USD, top coat 12 m²/L ×2 coats, 15 L can, 145 USD
Output Required paint 40.48 L / 3 cans / $388.00 / leftover 5.52 L
Paint Quantity, Can Count, and Estimated Cost Calculator
Enter area, coats, substrate roughness, waste rate, and product-specific coverage to calculate required paint, can count, and estimated cost in one pass.
It is a standard calculator that works for both B2C and B2B. m²/ft², L/gal, and currency switching are built in from the start.
Switch between m²/ft² and L/gal from the start
Calculate coverage, coats, roughness, and waste together
Use currency switching and share URLs for global teams
How to use
- Choose the unit system, then select the currency and enter the area.
- Set the substrate roughness factor and waste rate. Use a preset if it fits.
- Add one row per product and enter coverage, coats, pack size, and unit price.
- Review required paint, can count, estimated cost, and leftover, then copy the result or share the URL.
Formulas
Each row is calculated independently and then summed. Can count is always rounded up.
- Required paint per row = area × coats × roughness factor × (1 + waste rate) ÷ coverage
- Can count = ceil(required paint ÷ pack size)
- Order quantity = can count × pack size
- Leftover = order quantity - required paint
- Estimated cost = can count × unit price
Sample calculations
Imperial example
Input Area 2,500 ft², roughness factor 1.10, waste rate 10%, exterior finish 400 ft²/gal ×1 coat, 5 gal can, 119 USD
Output Required paint 7.56 gal / 2 cans / $238.00 / leftover 2.44 gal
Glossary
- Area
- The surface area you plan to paint. Enter it in m² or ft².
- Coverage
- The manufacturer's guideline for how much area one unit of paint can cover.
- Coats
- The number of times the same product is applied, such as primer, intermediate, or top coat passes.
- Roughness factor
- A multiplier that increases the required amount when the substrate is uneven or absorbent.
- Waste rate
- A percentage allowance for splatter, roller holdout, and leftover in the container.
- Pack size
- The purchase size per can or pail. The tool rounds up to this unit.
Notes
This tool provides planning estimates. Always follow the site conditions and the manufacturer's specifications.
- The actual amount changes with substrate condition, weather, humidity, and application method.
- Can count is rounded up, so leftover is expected in many cases.
- Check whether the product coverage is listed before dilution or after dilution before you enter it.
FAQ
Should I enter coverage in m²/L or ft²/gal?
Match the selected unit system. When you switch the unit system, the area, coverage, and pack size are easier to keep aligned in the same unit family.
What should I use for the roughness factor?
Use about 1.00 for a smooth substrate and 1.10 or higher for absorbent or uneven surfaces, then adjust to the product sheet and site conditions.
Why is can count rounded up?
Paint is usually bought in whole cans or pails, so the calculator rounds up to the smallest purchasable unit that covers the need.
Can I switch currencies?
Yes. You can switch between JPY, USD, EUR, and other common currencies so the same estimate can be reviewed in different markets.
Can a share URL reproduce the same inputs?
Yes. The share URL button copies a URL that includes the current state.