Charcoal Calculator — Sticks, Pencils & Fixative

This calculator estimates charcoal materials using surface area and coverage rates per stick type.

Units needed = (Total area / Coverage per unit) x Wastage factor

Coverage rates used

• Willow charcoal: ~800 cm² per stick
• Vine charcoal: ~1000 cm² per stick
• Compressed charcoal: ~600 cm² per stick
• Charcoal pencils: ~400 cm² per pencil

These are house estimates for medium-pressure shading, not manufacturer figures — no standardised coverage rate exists because usage swings widely between light sketch lines and heavy side-of-stick fills. Denser sticks (compressed) and hard points (pencils) cover less area per unit. If your technique is heavier or lighter than average, enter your own rate with the Custom option. The defaults sit at the consistent end and round up, so they err toward over-ordering rather than running short.

Fixative coverage is based on approximately 20,000 cm² per 400 ml can — a conservative figure for heavy charcoal. Many 400 ml aerosol fixatives cover nearer 30,000-40,000 cm² (3-4 m²) on lighter work; adjust the coverage figure in Advanced Options to match your can and how heavily you spray. Choosing a different can size scales the coverage in proportion to its volume.