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Metric to Imperial Length Conversions
Quick-reference conversion table for millimetres, centimetres and metres to inches, feet and yards. Common UK construction lengths in both units.
Fundamental Conversion Factors
| From | To | Multiply By |
|---|---|---|
| Inches | Millimetres | 25.4 |
| Millimetres | Inches | 0.03937 |
| Feet | Metres | 0.3048 |
| Metres | Feet | 3.2808 |
| Yards | Metres | 0.9144 |
| Metres | Yards | 1.0936 |
Common Construction Lengths
| Metric (mm) | Imperial | Common Use |
|---|---|---|
| 6 | 1/4" | Plywood thickness, tile spacer |
| 10 | 3/8" | Mortar joint thickness |
| 12.5 | 1/2" | Plasterboard thickness |
| 15 | ~5/8" | Copper pipe OD |
| 22 | ~7/8" | Copper pipe OD |
| 25 | ~1" | Timber batten thickness |
| 50 | ~2" | Insulation board, timber thickness |
| 100 | ~4" | Block width, concrete slab |
| 150 | ~6" | DPC height, joist depth |
| 215 | ~8.5" | Brick length (standard UK) |
| 300 | ~12" (1ft) | Rule of thumb: 300mm ≈ 1 foot |
| 600 | ~24" (2ft) | Standard joist/stud spacing |
| 900 | ~36" (3ft) | Door width, worktop height |
| 1200 | ~4ft | Sheet material width |
| 1800 | ~6ft | Fence panel height, shortest timber |
| 2100 | ~7ft | Standard door height |
| 2400 | ~8ft | Sheet material length, ceiling height |
| 3000 | ~10ft | Common timber length |
| 3600 | ~12ft | Common timber length |
| 4800 | ~16ft | Long timber length |
Inches to Millimetres — Quick Reference
| Inches | mm | Inches | mm |
|---|---|---|---|
| 1/8" | 3.2 | 4" | 101.6 |
| 1/4" | 6.4 | 5" | 127.0 |
| 3/8" | 9.5 | 6" | 152.4 |
| 1/2" | 12.7 | 8" | 203.2 |
| 3/4" | 19.1 | 10" | 254.0 |
| 1" | 25.4 | 12" (1ft) | 304.8 |
| 2" | 50.8 | 24" (2ft) | 609.6 |
| 3" | 76.2 | 36" (3ft) | 914.4 |
Related Pages
See the Area Conversions, Volume Conversions, and Weight Conversions. Use the Metres to Feet Converter to convert a length without reading off the table.
Next up: related pages
Frequently Asked Questions
There are exactly 25.4mm in one inch. This is the fundamental conversion factor for all metric/imperial length conversions. 1 foot = 304.8mm, 1 yard = 914.4mm, 1 metre = 39.3701 inches. In UK construction, materials are manufactured to metric dimensions but many tradespeople still think in feet and inches — particularly for room sizes, timber lengths, and pipe runs.
The most commonly encountered construction lengths are: 2440mm = 8 feet (standard sheet size length), 1220mm = 4 feet (standard sheet width), 2400mm = common stud wall height, 600mm ≈ 2 feet (joist/stud spacing), 300mm ≈ 1 foot, 100mm ≈ 4 inches. Plasterboard comes in 2400 x 1200mm sheets (close to 8 x 4 feet), timber is sold in 300mm increments from 1.8m to 6.0m.
The UK construction industry metricated in the 1970s. Sheet materials (plywood, plasterboard, OSB) are manufactured to metric sizes — 2440 x 1220mm is not exactly 8 x 4 feet (which would be 2438.4 x 1219.2mm) but is close enough to be interchangeable. Some imported products retain exact imperial sizes. Timber is sold by metric cross-section (e.g., 47 x 100mm) but often in imperial-derived lengths (2.4m ≈ 8ft, 3.0m ≈ 10ft).
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Last updated: April 2026
Verified against UK standards · estimates only, confirm with your supplier.