How much wash do I need to mix?

Always mix more than you think you need — running out mid-wash creates a hard edge that is nearly impossible to fix. This calculator adds 50% extra as a safety margin. For large washes, err on the side of too much.

What is the difference between wash types?

A flat wash has even colour across the area. A graded wash transitions from strong to light (or vice versa). A variegated wash blends multiple colours. Graded and variegated washes use slightly more paint due to overlapping strokes.

How do I mix a wash correctly?

Put water in a clean container first. Add concentrated paint gradually, stirring thoroughly. Test on scrap paper. The colour should be slightly darker than desired — watercolour lightens by 20-30% when dry.

What dilution should I use?

Light washes (transparent tints) use about 5% paint to water. Medium washes (standard) use 10%. Strong washes (deep colour) use 20%. The more transparent the wash, the more water you need.

Can I save leftover wash?

Yes — store in a sealed container and it will keep for days. The pigment may settle — stir before reuse. Diluted washes are also useful for tinting subsequent layers or mixing new colours.

ArtCalcs

Wash Size Calculator — Watercolour Wash Volume

Calculate the volume of diluted watercolour paint needed for a flat or graded wash.

Wash Width

Wash Height

Wash Type

Dilution

How We Calculate This

How Wash Calculation Works

Solution volume = Area x Coverage rate x Wash type multiplier x 1.5 extra

The coverage rate depends on dilution (light, medium, strong). Graded washes need 20% more, variegated 30% more than flat washes. The calculator adds 50% extra because running out of wash mid-application is the most common watercolour mistake.

Frequently Asked Questions

Related Calculators

Watercolour Dilution Calculator

Calculate watercolour paint-to-water ratios for different wash strengths. Covers wet-on-dry, wet-on-wet, glazing and dry brush.

Paper Stretch Calculator

Calculate gummed tape length, soaking time and drying time for stretching watercolour paper. Covers different paper weights and sizes.

Masking Fluid Calculator

Calculate masking fluid needed for watercolour painting based on area to mask, coverage percentage and number of coats applied.

Colour Lift Calculator

Check which watercolour pigments are liftable, staining or non-staining and plan your painting layers for easier corrections.

Half Pan Calculator

Calculate how many paintings a half pan or full pan of watercolour will last based on your painting frequency and usage style.

Last updated: February 2026

All calculations are estimates. Always verify quantities before purchasing materials.