Tube Volume Calculator — Tubes to Pans Conversion

A standard 5 ml tube fills roughly 2-3 half pans once you allow for drying shrinkage, which matches what artists report in practice (Jane Blundell, Winsor & Newton). A 14 ml tube fills about 7 half pans. Tubes still work out better value than buying the same colour as ready-made pans.

Moist tube watercolour holds water and humectants (such as glycerin) that evaporate as the paint dries in the pan, so the cake ends up smaller than the wet fill. Factory quality-control figures (Paul Rubens, 2026) put the loss at roughly 20-25% by volume; lighter-binder brands sit lower. The remaining dry paint is denser and more concentrated, which is why this calculator defaults to retaining 78%.

Squeeze thin layers (about 1-2 mm) and let each layer dry completely before adding the next. For a half pan plan on 3-4 layers over roughly 6-8 days; a thick single fill shrinks unevenly and cracks. Work in a dust-free area and top up any dips after the final layer has set.

Common watercolour tube sizes: 5 ml (standard), 8 ml (some brands), 14 ml (large), and 37 ml (studio size). Artist grade is usually 5 or 14 ml. Student grade often comes in 8 or 12 ml tubes.

Tubes are almost always cheaper per ml of paint. A 5 ml Winsor & Newton tube costs roughly the same as a single 1.5 ml half pan, yet — even after drying shrinkage — yields close to 2-3 half pans of usable colour. Buy your most-used colours in tubes and refill pans yourself.