Imperial vs Metric: Which Is Better for Woodworking?
Ask a group of woodworkers whether they prefer inches or millimetres and you are likely to get a lively debate. Some have worked in feet and inches for decades. Others would not dream of making a cabinet or setting up a CNC router without using millimetres.
So which system is actually better for woodworking? The answer depends on the job, the tools you own and the measurements you work with every day.
Why metric works so well in a modern workshop
For furniture making, cabinetmaking and precision woodworking, metric measurements make everyday calculations simple. If a cabinet is 600 mm wide and is built with two 18 mm side panels, the internal width is 564 mm. There are no fractions to convert, and the figure can go straight onto your cutting list.
- Easy arithmetic: dimensions are added, divided and subtracted using decimal numbers.
- Modern workshop compatibility: millimetres are common on UK and European machinery, CNC routers and CAD drawings.
- Hardware compatibility: many hinges, runners, shelf-pin layouts and other cabinet fittings use metric dimensions.
- Repeatability: dimensions are straightforward to record and reproduce when making multiple parts.
The main drawback is compatibility with inch-based tools, cutters and American woodworking plans. Some divisions, such as splitting a length into thirds, also result in recurring decimals.
Why imperial still has a place
Imperial measurements remain especially popular among American woodworkers and in traditional woodworking. Fractions can be intuitive: half of 3/4 inch is 3/8 inch, and a 12-inch length divides neatly into halves, thirds and quarters.
- Familiar fractions: handy for woodworkers accustomed to 1/2, 1/4, 1/8 and 1/16-inch increments.
- Excellent US compatibility: many plans, router bits, fasteners and building materials use inch-based sizes.
- Useful divisibility: 12 inches can be divided into several common whole-inch increments.
However, calculations involving mixed fractions take more care. For example, adding 5/16, 7/32 and 3/8 inch is less immediate than adding three decimal measurements. And when working with metric hardware or suppliers, converting back and forth introduces another opportunity for error.
Putting both systems to work
Dividing a board
A 1,000 mm board divided into five equal sections gives exactly 200 mm each. A 39 3/8-inch board divided by five gives 7 7/8 inches each. Both systems work perfectly well here. The original boards are not precisely the same length: 39 3/8 inches is 1,000.125 mm.
Building a cabinet
With metric sheet material and hardware, working in millimetres usually makes the design process simpler. A 600 mm cabinet built from 18 mm sides leaves 564 mm internally. If the project starts with imperial-size material and drawings, using inches throughout can be equally sensible.
Marking out accurately
One sixteenth of an inch is 1.5875 mm, one thirty-second is 0.79375 mm, and one sixty-fourth is about 0.397 mm. A finely graduated imperial ruler may allow smaller marked increments than a metric ruler marked only in whole millimetres. This does not mean imperial is inherently more accurate. The measuring tool, your setup and your technique are what count.
Which is best for different woodworking jobs?
| Woodworking task | Most practical choice |
|---|---|
| UK and European cabinetmaking | Metric |
| CNC routing and CAD | Usually metric, although both are supported |
| Traditional hand-tool joinery | Either system |
| US construction and American plans | Imperial / US customary |
| Jigs, fences and repeat stops | Whichever matches the equipment |
| Precision work | Both can be equally accurate |
Is metric more accurate than imperial?
No. One inch is exactly 25.4 mm. Either unit can express a highly precise dimension. Accuracy depends on the tolerance specified, the tools used and the way the work is carried out, not whether the drawing says inches or millimetres.
Our verdict
For most modern UK woodworking workshops, metric is the most practical primary system. It makes calculations easier, works naturally with common cabinet materials and fittings, and is widely used in international manufacturing.
That does not make imperial wrong. If you build from American plans or use inch-based cutters and tools, imperial can be the most efficient choice for that particular job.
Our advice: pick one measurement system for the job and stick to it from design through to cutting and assembly. If you need to convert, keep the original measurement and label converted values clearly rather than mixing rounded figures.
What do you use in your workshop: metric, imperial or a mixture of both?
