Angle finder for skirting
Updated: 22 October 2026
You are fitting skirting in a UK house, the corner is not a clean right angle, and a 45° and 45° pair will open a gap you can see along the joint. An angle finder for skirting reads the corner between the two walls, at the height of the board, so you can turn that reading into a saw setting without halving the wrong number. The [angle finder comparison](/hub/measuring-and-marking-tools/angle-finder) lists the tools. This page is the geometry. Peter F. used the 19 October 2026 amazon.co.uk listings and UK fitting guides, including one Skirting4u worked example that disagrees with itself. There is no lab test. A qualifying purchase can earn a commission at no extra cost to you.
You are fitting skirting in a UK house, the corner is not a clean right angle, and a 45° and 45° pair will open a gap you can see along the joint.
You are fitting skirting in a UK house, the corner is not a clean right angle, and a 45° and 45° pair will open a gap you can see along the joint. An angle finder for skirting reads the corner between the two walls, at the height of the board, so you can turn that reading into a saw setting without halving the wrong number. The angle finder comparison lists the tools. This page is the geometry. Peter F. used the 19 October 2026 amazon.co.uk listings and UK fitting guides, including one Skirting4u worked example that disagrees with itself. There is no lab test. A qualifying purchase can earn a commission at no extra cost to you.
Our top picks
| Badge | Product | Finder type | Corner reading | Size | Note | Price | Offer |
|---|---|---|---|---|---|---|---|
| Best overall |  LEXIVON LEXIVON LX-230 mitre protractor | Mechanical protractor | Scales on two walls | 7 inch | 7.8 | about £19.99 | View offer |
| Alternative |  Trend Trend DLB digital level box | Magnetic angle box | No arms for a corner | 28 mm | 7.6 | about £19.95 | View offer |
| Best value |  Trend Trend DAR/200 digital angle rule | Hinged digital rule | Two arms on the walls | 200 mm | 7.4 | about £18.49 | View offer |
On this page
Put a hinged finder on the corner, not a box
The reading you need is the angle between two faces. A hinged digital rule or a mechanical protractor can sit with one arm on each wall. A magnetic box cannot. It reads the tilt of one surface after you zero it, which is a saw-blade job, and the full split is on angle finder vs angle box.
Seat both arms where the skirting will actually sit, not halfway up a bowed plaster line. Plaster buildup changes the angle above the board, so a reading taken at picture-rail height can be a different corner from the one the board has to fill. About 200 mm closed is the common arm length in this set, and that span is enough when both arms lie on the wall at skirting height. The Entatial listing is 500 mm, £32.50, with seven reviews. The extra length is not a reason to prefer it. Trend’s DAR/200 is best value at £18.49, and the bullets name skirtings, cornices and shelves. The LEXIVON LX-230 is the top pick at £19.99, and UK reviews describe inside angles and skirting. This page does not rank them. The LEXIVON has no digital screen, so you cannot halve a display by accident, and you can still halve the scale wrong.
An external 91° reading is not a 22.5° saw setting
Skirting4u’s external bisect article is the worked example to keep, and it disagrees with itself. The finder reads 91° on an external corner, then 180 minus 91 equals 89, then 89 divided by 2 equals 44.5° for each piece. The next step on the same page says set the mitre saw to 22.5° for that example. Do not set 22.5° because a finder read 91°. If 44.5° is the cut in the sense of that second step, prove the pair on offcuts before you shorten the finished lengths. A saw scale marked from square is a different zero from the wall angle. Turning the saw the wrong way will open the joint even when the arithmetic was right.
The square case is why halving feels safe. For a true 90° corner, half of 90 is 45, and half of the supplement is also 45. Halving whatever you measured only coincides with the right cut while the corner stays square. Checkatrade’s UK guide says the same thing without the sum: do not assume 90° in an older property, test the joint, and do not keep trimming the wrong face. The 91° case is the only worked example on this page.
Internal corners: scribe is the usual UK joint
Wickes, and the same habit in other UK trade guides, treats an ordinary internal skirting joint as a scribe. One board is cut square into the corner. The next is coped to the profile. A scribe can absorb a corner that is not square without a mitre sum, which is why those guides barely mention an angle finder for internal skirtings. This page is not a coping-saw tutorial. If you are scribing, you do not halve a screen at all.
If you still mitre an internal corner, you have to know whether the number in your hand is the wall angle or the figure the saw wants. A LEXIVON UK guide, as recorded for this category, treats a 96° internal corner as 48° each. That is halving the wall angle. It is not the external path, which went through 180 minus the reading before the half. These searches did not lock a second formula you should memorise. If you are unsure which way the saw scale runs, the offcut is the check. An external 44.5° pair will not close an internal joint.
Prove it on offcuts of the same board
Cut a short pair from the same skirting before you cut the lengths that have to reach the next corner. Hold them in the real corner, at the height the board will sit, and look at the face and the top edge. If the joint opens, you have learned the direction of the error while the waste is still a scrap. Checkatrade’s warning applies here: trimming the wrong face makes the gap worse and shortens a board you cannot put back.
A rule of thumb, not a measurement from this set: 0.5° on a 100 mm width is about 0.9 mm of gap. On a deep Victorian ogee that is enough to see. On a narrow modern board it is still a dark line. The point of the figure is scale. It is not a reason to chase 0.05° on a screen whose stated band is ±0.5°. The angle finder buying guide is where that distinction is set out.
Stop and call a joiner when the piece is a structural stair, or when the rail is a barrier rather than a decorative trim. A wrong mitre on a landing handrail is not the same waste as a short offcut behind a sofa.
Common questions
My corner is not 90°. What do I set the saw to?
Read the corner with a hinged finder at skirting height, then decide whether that number is the wall angle or the saw angle. For the external example on this page, a 91° reading is worked as 180 minus 91, then half, which is 44.5° on each piece. Prove the pair on offcuts before you cut the long boards.
The finder says 91°. Is the cut 45.5°, 44.5°, or 22.5°?
For that external example, the arithmetic that matches the article’s second step is 44.5° on each piece: 180 minus 91 is 89, and half of 89 is 44.5. Halving 91 itself is 45.5, which is the habit that only works while the corner is square. The same article then says 22.5°. Do not copy 22.5° for a 91° reading. Cut offcuts and see which face closes.
What is different for an internal corner and an external corner?
An external corner is the one you usually mitre, and the 91° example on this page is that case. An internal corner, in Wickes-style UK guides, is usually scribed: one board square into the corner, the next coped to the profile. A scribe does not need the 180-minus sum. If you mitre internally anyway, a 96° wall halved to 48° each is a different operation from the external path, and you still have to match the saw scale.
Should I mitre an internal skirting joint or scribe it?
UK fitting guides generally scribe ordinary internal skirtings, because the cope follows the profile and tolerates a corner that is not square. Mitre the external corners. A mitre on an internal joint is possible, and it is where the halving trap sits, so use it when you have a reason and an offcut that already closed. This page does not walk through a coping-saw sequence.
Can I use a magnetic angle box in the corner?
No. A magnetic box, including a laser box, reads the tilt of one face after a zero. It has no two arms to lay on two walls, so it cannot take the skirting reading. Use it on a saw blade or a fence. The corner reading stays with a hinged rule or a mechanical protractor.
When is a stair or a handrail no longer a DIY mitre?
When the stair is structural, or when the handrail is a barrier rather than a trim you can lift off, stop and use a joiner. A test offcut is the right check for a skirting run in a living room. It is the wrong place to discover that a guarding rail is short or open. Decorative cornice and shelves stay in the same measuring habit as the skirting, with the same offcut before the finished length.
Related pages
Sources
Public UK sources from the digest first, then the amazon.co.uk listings compared on this page. Prices and stars were taken on 19 October 2026.
- Trend UK DAR/200 (retrieved 19 October 2026)
- Trend INST/DAR (retrieved 19 October 2026)
- GOV.UK: button and coin batteries (retrieved 19 October 2026)
- BSI PAS 7055:2025 (retrieved 19 October 2026)
- Child Accident Prevention Trust: button batteries (retrieved 19 October 2026)
- Great Ormond Street Hospital: button batteries (retrieved 19 October 2026)
- Consumer Rights Act 2015, section 22 (retrieved 19 October 2026)
- Skirting4u: external bisect (retrieved 19 October 2026)