Timber Calculator

Understanding Tongue & Groove

If you’ve ever bought T&G cladding or flooring, you’ll have noticed two measurements on the label: the Total Width (also called the nominal width) and the Face Cover. They’re different — and the difference matters when you’re working out how many boards you need.

Board 1 Board 2 TONGUE GROOVE TOTAL WIDTH (NOMINAL) FACE COVER (VISIBLE WIDTH) tongue fits into groove →

The Total Width is the full width of the board as it comes off the saw — tongue and all. The Face Cover is the bit you actually see once the boards are fitted together. The tongue disappears into the next board’s groove, so you lose a few millimetres per board. That’s why you always need more boards than a simple area calculation would suggest.

Joiner’s Tip

Always use the Face Cover measurement — not the Total Width — when calculating how many boards you need. If you use the Total Width, you’ll end up short. Select your product from the dropdown and the calculator handles this for you automatically.

How to Use This Calculator

1

Measure Your Wall Area

Grab a tape measure and note the width and height of the area you want to cover, in metres. Multiply them together to get the total area (Width × Height = m²). If you’ve got multiple walls, measure each one separately and add the results up — or run the calculator once per wall.

2

Choose Your Timber

Use the Select Product dropdown at the top of each section. When you pick a product, the calculator auto-fills the board dimensions and price per metre for you — no need to look up spec sheets. If you’re using something we don’t list, just choose “Custom / Manual Entry” and type the numbers in yourself.

3

Check the Waste Factor

The waste factor is set to 10% by default. This accounts for offcuts, mistakes, damaged boards, and the odd measurement error — it’s standard practice in the trade. For complex layouts with lots of angles or openings (windows, doors), consider bumping it to 12–15%. For a simple rectangular wall, 10% is spot on.

Joiner’s Tips

Cladding & Flooring

When ordering cladding, always buy from the same batch where possible. Timber is a natural product — colour and grain can vary between batches, especially with species like Siberian Larch and Western Red Cedar. If you’re covering a large area, it’s far better to over-order slightly than to try and colour-match later.

Battens & Carcass

When measuring for battens, remember to account for vertical airflow if you’re cladding externally. Building regs typically require a ventilated cavity behind the cladding boards, so your battens need to be deep enough to allow air to circulate (usually 25–38 mm). Space them at 400–600 mm centres depending on your board thickness.

Trims & Beading

The trims calculator includes a 5% mitre waste factor automatically. Mitre cuts at corners always produce offcuts you can’t reuse, and trimming is fiddly work where mistakes happen. For internal corners, consider using a scribing technique instead of mitres — it’s more forgiving and gives a cleaner finish over time as the timber moves.

General

Timber should be acclimatised before fitting. Store your boards flat in the room (or near the site) for at least 48 hours before installation. This lets the moisture content equalise with the environment, reducing the risk of shrinkage, cupping, or gaps appearing after fitting. This applies to all timber products — cladding, flooring, and trims alike.

Timber & Cladding Calculator

Professional calculation tool for builders, joiners, and serious DIYers

Global Settings

Area-Based Calculation

Linear-Based Calculation

Perimeter Calculation

Includes 5% waste factor for mitre cuts automatically.

Hawksbury Timber

Timber Estimate

Cladding & Flooring

Battens & Carcass

Trims & Beading

Project Totals

Total Area:
Total Linear Metres:
Estimated Weight:
Estimated Cost:

Disclaimer: This is an estimate based on provided dimensions. Linear metres are calculated using whole lengths. Please verify all measurements before cutting.