Paint Calculator: Liters & US Gallons

Estimate how much paint you need from the net surface area, the planned coats, and the coverage stated for your product. Calculate liters or US gallons, and optionally estimate whole containers using the container size you plan to buy.

Calculate paint needed

Enter the total area you intend to paint, after any openings you choose to exclude. Use the product's coverage and check whether it applies to one coat or the complete coating system. This tool does not choose a coverage rate.

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How to calculate how much paint you need

When coverage is stated for one coat:

Paint quantity = net paintable area x coats / coverage per unit for one coat

For an illustrative 600 square feet, 2 coats, and a product coverage of 300 square feet per US gallon per coat, 600 x 2 / 300 = 4 US gallons. This coverage value is an example, not a universal product rate.

For measurement steps and worked examples, read our guide to calculating how much paint you need.

Avoid counting coats twice

If your product information instead states how much area one unit covers for the entire planned coating system, use area / complete-system coverage. Do not multiply by coats again. Changing the coverage basis in the form clears the coverage field so you can enter the corresponding value.

For example, a complete-system coverage of 150 square feet per US gallon over the same 600-square-foot project gives 600 / 150 = 4 US gallons.

Measure wall area, not floor area

For each rectangular wall, multiply its width by its height and add the walls. Subtract door or window areas if you intend to exclude them from the painted area. Add a ceiling only if it uses the same product, coverage, and coating plan. Floor square footage alone does not determine wall area.

Use our Square Footage Calculator for rectangular wall sections; enter wall height as one of the dimensions. This paint calculator does not automatically subtract openings.

Metric paint example

With 50 square meters, 2 coats, and coverage of 10 square meters per liter per coat: 50 x 2 / 10 = 10 liters. If you choose 2.5-liter containers, that is 4 containers. Use your product's real coverage rather than treating this example as a recommendation.

Liters and US gallons

One US liquid gallon equals exactly 3.785411784 liters. This calculator uses US gallons, not Imperial gallons. Make sure coverage rates and container sizes use the selected units.

Frequently asked questions

Does the result include primer?

No. Calculate primer separately using its own area, coat count, and coverage. Different paints or finishes should also be calculated separately.

What if the label provides a coverage range?

Choose a coverage value appropriate to your substrate and application according to the manufacturer's guidance. A lower coverage value requires more paint. You can run separate calculations for the low and high ends to compare quantities.

Does container rounding add a waste allowance?

No. It rounds up to whole containers of the size entered. It does not add an extra percentage for losses, storage, or future touch-ups.

What affects actual paint usage?

Surface texture, porosity, preparation, color change, application method, and product instructions can affect coverage. Confirm your assumptions with the manufacturer or supplier.

Can I calculate several products together?

Only combine areas that use the same product and coating assumptions. Calculate walls, trim, ceilings, primer, or different finishes separately when their coverage or coats differ.

What happens when I change units?

Area, coverage, and container size clear to prevent mixing units. Enter the values again in the selected system. The coverage basis and coat count remain selected.

What inputs are supported?

Positive area up to 10,000,000, coverage up to 100,000, and optional container size up to 100,000 in displayed units. Up to four decimal places are accepted using a decimal point or comma, without thousands separators. For per-coat coverage, enter 1 to 20 whole coats. With complete-system coverage, the separate coat field is ignored and disabled.

HandyMetric provides general quantity estimates, not painting specifications, guaranteed coverage, or contractor quotes. Check measurements and product instructions before purchasing.