Fence & Shed Paint Calculator

Updated October 2026

Quick answer: For ten panels measuring 6ft × 6ft, painted on both sides with two coats, allow about 22.3 litres at 6m² per litre. That means five 5-litre tubs. Rough, weathered timber can absorb more, so check a small test area and replace the calculator's coverage and price with the figures for your chosen treatment.

How to measure fence panels

Measure the width and height of the timber actually being painted, rather than assuming every “6ft panel” is square. Many panels are approximately 1.83m wide but only 0.9m, 1.2m or 1.5m high. Concrete posts and gravel boards should be excluded if they are staying unpainted. Add wooden posts, rails and gates separately where they materially increase the surface.

For matching panels, multiply panel width by panel count to obtain the calculator's total length. Select one side or both sides as appropriate. Do not double the length and also select both sides, as that counts the second face twice. For mixed heights, calculate each section separately and add the litres before rounding to whole tubs.

Feather-edge and overlap boards have edges and recesses beyond their flat rectangular footprint. A nominal area is still a useful starting point, but a lower coverage rate usually gives a more realistic estimate. You also need permission and practical access before painting a neighbour-facing side.

Measuring a shed

Add the lengths of all four exterior walls and enter their average rectangular wall height. For a 2.4m × 1.8m shed with 1.8m-high eaves, the wall run is 2 × (2.4 + 1.8) = 8.4m and rectangular area is 15.12m². Two triangular gables, each 1.8m wide and 0.45m high, add 0.81m², giving 15.93m².

For that shape, entering an equivalent length of 15.93 ÷ 1.8 = 8.85m at 1.8m high reproduces the full area. Select one side for exterior shed walls. Deduct large windows if worthwhile; paintable doors remain included. Fascias, bargeboards and a timber roof need separate measurement. Do not include felt roofing in a timber-paint calculation.

These are indicative ranges, not product claims. A label may give a maximum on a favourable surface, whereas dry, absorbent wood and detailed edges use more. The calculator defaults to 6m²/L and applies the same rate to every coat. It does not automatically improve the second-coat coverage or add spraying losses.

Worked example: ten 6ft panels, both sides

1. Convert 6ft to approximately 1.8288m. Ten panels give a run of 18.288m.
2. Area on one side is 18.288 × 1.8288 = 33.45m².
3. Both sides give 33.45 × 2 = 66.89m².
4. Two coats require 66.89 × 2 = 133.78m² of coat coverage.
5. At 6m²/L, 133.78 ÷ 6 = 22.30 litres.
6. Round 22.30 ÷ 5 up to five tubs. At the calculator's example price of £18 each, paint costs £90.

Rounding already provides 2.7 litres above the nominal requirement. At a less favourable 4m²/L, the same job requires 33.45 litres, or seven 5-litre tubs costing £126 at that illustrative unit price. Coverage has a bigger effect here than a small price difference between tubs.

Coats, preparation and application

Two coats are a sensible starting point for many coloured fence treatments, but follow the actual instructions. A one-coat formulation, a drastic colour change or a very absorbent surface needs its own assessment. The first coat should dry for the specified interval; painting over a wet coat can produce an uneven finish.

Brush away debris and algae, remove loose coating and let the timber dry after cleaning. Repair rotten boards rather than concealing them. Work paint into edges and end grain without flooding gaps. Protect plants, paving, glass and neighbouring property, and pick a dry period within the coating's temperature limits.

Brushing or a pad offers control around overlap joints. Spraying can be quicker on large runs but overspray and wind increase losses. If you expect 10% application loss in the worked example, 22.30 × 1.10 = 24.53 litres still fits five tubs. A 15% loss would exceed 25 litres and require another tub.

DIY cost versus paying someone

These are typical UK ranges, never quotes. A long run painted both sides can take more than a day once cleaning, drying, access and two coats are included. Ask whether a panel price includes one face or two, posts, gates, preparation and paint. Do not compare a one-face quick spray with a fully brushed two-coat job.

Use the calculator above to compare tub prices and coverage. For preparation and labour decisions, read DIY versus hiring a tradesperson; for ways to avoid unnecessary extra coats, see painting mistakes that waste money. Both help turn the paint quantity into a practical job plan.

Frequently asked questions