Art and Craft Supplies
Gesso and varnish amount.
Size, coats and the coverage printed on the tin or bottle are enough to know how much to buy. The calculator ships no coverage figure of its own, so it uses yours.
Volume = area x coats / coverage, plus waste. A 24 x 36 in panel (6 sq ft), 2 coats, a label that says 400 sq ft per US gallon and 10% waste needs 125 mL (4.2 fl oz).
Surface and product
Amount to buy
Fill the form and press Calculate.
Worked example
A 24 x 36 in panel is 864 sq in = 6 sq ft. Two coats make 12 sq ft of coating. The label example says 400 sq ft per US gallon, which is 400 x 0.09290304 / 3.785411784 = 9.82 m2 per litre. The volume is 12 sq ft = 1.115 m2, divided by 9.82 = 114 mL, and with 10% waste 125 mL (4.2 fl oz). Coating a 1.5 in deep edge as well adds 1.25 sq ft and takes the amount to 151 mL. In metric, four 60 x 90 cm panels with 3 coats at an example label of 8 m2 per litre need 891 mL.
How it works
One coat covers the surface area once, so the volume is the area times the number of coats divided by the coverage, then increased by a waste allowance. The coverage is the figure from the label, because it varies by product, by thickness and by how absorbent the surface is.
To convert a US label figure, 1 sq ft is 0.09290304 m2 and 1 US gallon is 3.785411784 litres. Edges are added as two long and two short strips of the depth you give.
Sources and basis (opened 2026-10-08): 1 sq ft = 0.09290304 m2 from Square foot (Wikipedia); 1 US gal = 3.785411784 L from Gallon (Wikipedia); 1 US fl oz = 29.5735295625 mL from Fluid ounce (Wikipedia); 1 in = 2.54 cm from Inch (Wikipedia). Coverage is entered from the product label; the 400 sq ft per gallon and 8 m2 per litre values are examples only.
FAQ
How much gesso do I need for a canvas?
Area x coats / the coverage on your gesso label. A 24 x 36 in panel at 2 coats with an example coverage of 400 sq ft per US gallon needs about 125 mL including 10% waste.
How much varnish for a painting?
Use the same sum with the varnish coverage from its label and the coats you plan. Many varnishes are applied thin, so check the label for coats and thinning.
Should I include the edges?
If you coat them, yes. For a 1.5 in deep edge on the example panel it adds 1.25 sq ft per coat.
What coverage should I enter?
The figure printed on the product, in sq ft per gallon or m2 per litre. The calculator deliberately has no built-in number, because it varies by brand and product.
Is 10% waste enough?
It is a rule of thumb. Rough, absorbent or textured surfaces can need more, so raise the allowance for those.
Disclaimer
Results are arithmetic from the numbers you enter. The result depends entirely on the coverage you enter. Follow the product label for coats, drying time, ventilation and safety.