Speed square buying guide
Updated: 22 October 2026
You are stood in a UK garage with a millimetre tape, a length of 4x2, and a speed square buying guide that keeps showing American rise-per-12 tools. The useful checks come before the brand. Match the scale to the tape, then the leg to the board, then the lip and the marks to the cut you actually make. Prices below are the amazon.co.uk shelf prices captured on 19 October 2026, from about £4.69 to £29.79, and they are not a lab ranking. The [speed square comparison](/hub/measuring-and-marking-tools/speed-square) lists all twelve. This page is the order of checks. Peter F. read those listings. No laboratory test. A qualifying purchase can earn us a commission at no extra cost to you.
You are stood in a UK garage with a millimetre tape, a length of 4x2, and a speed square buying guide that keeps showing American rise-per-12 tools. The useful checks come before the brand.
You are stood in a UK garage with a millimetre tape, a length of 4x2, and a speed square buying guide that keeps showing American rise-per-12 tools. The useful checks come before the brand. Match the scale to the tape, then the leg to the board, then the lip and the marks to the cut you actually make. Prices below are the amazon.co.uk shelf prices captured on 19 October 2026, from about £4.69 to £29.79, and they are not a lab ranking. The speed square comparison lists all twelve. This page is the order of checks. Peter F. read those listings. No laboratory test. A qualifying purchase can earn us a commission at no extra cost to you.
Our top picks
| Badge | Product | Scales | Size | Drill gauge | Note | Price | Offer |
|---|---|---|---|---|---|---|---|
| Best overall |  Preciva Preciva speed square, black | Metric | 180 mm | 3–15 mm | 8.6 | about £8.49 | View offer |
| Alternative |  Swanson Swanson speed square kit, 7 inch and 12 inch | Imperial | 7 and 12 inch | n/a | 8.0 | about £21.84 | View offer |
| Best value |  Difistik Difistik speed square, 7 inch | Metric | 178 mm | 3–15 mm | 7.4 | about £6.99 | View offer |
On this page
Match the scale to the tape
A UK cutting list is in millimetres, and a roof pitch on a drawing is usually a degree. The first check is whether the ruler on the triangle is that language. A famous name does not settle it. Swanson SW1201K, the 7 inch and 12 inch pair at about £21.84 with 4.6 from 10,068 reviews, is rise per 12 inches. That pair is the right language only when you are copying that imperial pitch on purpose. If the tape in your hand reads 38 mm or 1,200 mm, those pitch numbers are not a measurement you can transfer.
A title that says 7 inch is a trade size, not proof of an inch scale. Several metric triangles in this set are sold as about 180 mm and still wear a 7 inch name, including the Difistik at about £6.99, both Preciva singles, and the DeWalt 18 cm square at about £16.25. The working scale on those listings is metric. Navoys, at about £4.69, does not settle the nickname: the title says 7 inch and one bullet says 6 inch, and the bullets never name millimetres or inches as the unit. Until those lines agree, the lowest price is not a choice you can check. If a new square’s title says metric and the scale in your hand is imperial, the Consumer Rights Act 2015 is the hook for “as described”, not a British Standard grade. None of these twelve listings shows BS 939 or BS 3322. The unit fork is on metric vs imperial speed square.
Pick the leg for the board, not the brand
Leg length is how much board you can mark or fence in one pass. About 110 mm stays in a pouch. The Tracer ASQ4M is that size, 110 mm and 80 g, at about £9.99 with 4.6 from 102 reviews, and UK reviews use it on smaller sections such as 4x2 and 3x2. It will not reach across a wide board as a saw fence. About 180 mm, the size most of these listings call 7 inch, covers belt work and ordinary carcass timber. About 300 mm, the 12 inch trade size, is the wide board and the longer fence.
You do not need both until the job asks for both. A metric 180 mm square is the usual single buy. Pairs in this set put about 180 mm and about 300 mm in one box: the OX set at about £29.79, and the Flintronic pairs at about £17.99. The inch names on those pairs are still the trade sizes. Read the scale line, which on OX and Flintronic is metric, before you treat “12 inch” as an imperial ruler. Swanson’s pair is the one that is imperial on both sizes. If you only cross-cut 4x2 and mark kitchen shelves, the 300 mm square is the bulky one in the bag. Buy the pair when you already know you will fence a wider board this month.
Lip, marks, and holes
The lip, the T-shaped base, is what you press to the timber and what a saw shoe can run against for a short cut. A thin or light body is a poor fence on heavy board. Shared Flintronic reviews argue about that: one says the 18 cm square bends more easily than the 30 cm square. Difistik’s 16 UK reviews include a buyer who found it less sturdy than expected and a corner that arrived rounded. DeWalt’s amazon.co.uk bullets, on DWHT25227-0 at about £16.25, are the listing in this set that says extra-thick extruded aluminium and a fixed large base. That is a claim on the page, not a thickness we measured.
How the marks are made is the next materials check. Laser-etched is what YANJINGSHE states, and what the OX bullets state. Stamped is what DeWalt states. Two UK reviews of the Tracer say the numbers are printed and may wear. Printed marks are the ones to doubt in a pouch full of bits. OX’s own site says laser-etched marks are twice as accurate as stamped marks. That sentence is the manufacturer’s. It is not a result from this set. Holes from 3 mm to 15 mm, listed on Preciva and Difistik, are a drill gauge. They are not a named screw standard, and they are not the scribe notches you drag a pencil through. YANJINGSHE sells the opposite body, a single piece with no holes, and says so. The flip test is on how to use a speed square.
What the listing does not prove
Stars are the amazon.co.uk line, not a calibration. Preciva’s black 180 mm square shows 4.7 from 1,185 reviews at about £8.49. YANJINGSHE shows 5.0 from 6. The larger count tells you more people have used a metric triangle at that price. It does not tell you the body is square to a tenth of a millimetre. A seller line of ±0.2 mm on the black Preciva bullets is seller text. It is not BS 939:2007, which covers engineers’ try squares, and it is not BS 3322:1981, which covers carpenters’ squares and sliding bevels. None of the twelve listings prints either grade.
Three Flintronic colour ASINs at about £17.99 share one 360-review text. You cannot add 360 three times, and you cannot treat red and black as separate trials. Inside that shared text, one review says the large square is out by 0.7 mm and one says the smaller width scale is printed about 1 mm offset. The OX listing at about £29.79, 4.8 from 730, mixes twin-pack notes with notes that read like a cheaper single square. The amazon model string is OX-P712301-E. The OX UK site’s 180 mm page uses OX-P634701, so do not paste the site’s accuracy sentence onto this set. A rule of thumb, not a measured tolerance: if a flip test passes and the work is millimetres, a metric 180 mm square under £17 is enough until you need a 300 mm fence or hip-and-valley scales.
Common questions
Should a UK buyer pick millimetres or inches?
Pick millimetres when your tape and drawings are in millimetres. Pick rise per 12 inches only when that is the pitch language you are following on purpose. Swanson SW1201K at about £21.84 is the imperial pair in this set. A 7 inch name on a metric triangle is the trade size, not the ruler. The full fork, including a metric Swanson that is not this ASIN, is on the metric-versus-imperial page.
Is 110 mm, 180 mm, or 300 mm the right leg?
110 mm, such as the Tracer at 80 g, stays in a pouch and suits smaller sections. About 180 mm covers ordinary belt work and 4x2. About 300 mm reaches a wider board and gives a longer saw fence. Buy a pair when you need both in the same week. The inch nickname on a metric 180 mm square does not turn the scale into inches.
What is the lip for, and when is a thin body a poor saw fence?
The lip hooks the edge so the leg can mark 90° or the hypotenuse can mark 45°, and a saw shoe can run against it for a short cut. It is not a guard. A thin or light body is a poor fence on heavy timber. Shared Flintronic reviews include a bend note on the 18 cm square and a thin-body argument. DeWalt’s bullets are the ones that say extra-thick. Keep the handheld guard on either way.
Are laser-etched marks better than stamped or printed ones?
Etched or stamped marks are the durable claim when the listing says so. YANJINGSHE and OX say laser-etched. DeWalt says stamped. Two Tracer reviews say the numbers are printed and may wear. Nothing here proves etched marks never wear, and OX’s “twice the accuracy” line is the manufacturer’s claim, not a test we ran. If the marks look pale after a week in the bag, that is wear, not a calibration.
Do 3–15 mm holes match a screw standard?
No standard is named on these listings. Preciva and Difistik list 14 diameters from 3 mm to 15 mm as a drill gauge. That is useful when you are picking a bit. It is not a scribe scale, and it is not a screw specification. YANJINGSHE states a solid body with no holes, which is the right buy only if you do not want that gauge.
Does a star rating mean the square meets BS 939?
No. Stars are the amazon.co.uk review line. BS 939:2007 is for engineers’ try squares and BS 3322:1981 is for carpenters’ squares and sliding bevels. None of these twelve listings shows either grade. A ±0.2 mm sentence on a bullet is not that grade. A failed flip test is a reason to stop, including on a structural cut, whatever the star line says.
What if the title and the bullets disagree on size?
Do not buy that row until you know which line is the tool. Navoys at about £4.69 says 7 inch in the title and 6 inch in one bullet, and it never names the unit system. The dimensions field, 25.4 x 17.8 cm, does not settle it. One UK review calls it solid and describes no defect, which still does not tell you the length. The Consumer Rights Act 2015 is the route if a square you have already bought is not as described.
Related pages
Sources
Public sources listed below. Prices and star lines are from the twelve amazon.co.uk listings captured on 19 October 2026.
- Swanson, Reading the Speed Square (retrieved 19 October 2026)
- OX Tools UK, 180 mm metric rafter square (retrieved 19 October 2026)
- DeWalt UK, DWHT25227-0 180 mm metric speed square (retrieved 19 October 2026)
- HSE, WIS16 Circular saw benches (retrieved 19 October 2026)
- BSI, BS 3322:1981 Carpenters' squares and bevels (retrieved 19 October 2026)
- BSI, BS 939:2007 Engineers' squares (retrieved 19 October 2026)
- legislation.gov.uk, Consumer Rights Act 2015 (retrieved 19 October 2026)
- Eden District Council, Pitched-roof timber sizes (retrieved 19 October 2026)