Torpedo Levels: The Pocket-Size Spirit Level for First Fix and Tight Spots

An electrician trying to check a back box with a 600mm level in a stud wall bay that's 400mm wide has a problem. A plumber trying to read a 1:40 fall on a short length of copper in a joist void has the same problem. The full-size spirit level is too long, and the wrong tool in a cramped spot is no tool at all.

The torpedo level is the answer. Around 230mm long, tapered at both ends, usually magnetic, and designed to slip into a tool belt pouch. Plumbers and electricians call it a boat level. Some homeowners call it a pocket level or mini spirit level. Same tool.

What almost nobody explains is that a torpedo is not a small version of a full-size level. It's a different tool for different jobs, and the rules for buying and using one are different. The wrong torpedo costs you accuracy where it matters most, and the right torpedo on its own still isn't enough.

What a torpedo level is

A torpedo level is a compact spirit level, typically 220 to 250mm long, with a tapered profile that lets it sit in awkward spaces. The body holds two or three vials (small glass or acrylic tubes filled with a dyed alcohol-based fluid and an air bubble): one for horizontal, one for plumb (vertical), and usually a third set at 45°.

The base is the feature that separates a torpedo from a shortened full-size level. Most trade torpedoes have a V-shaped groove milled into the bottom edge, which cradles round pipes and conduit so the level doesn't roll. Most also have rare-earth magnets embedded in the base, strong enough to hold the level against a steel back box, a radiator valve, or a copper pipe so you can step back and read it with both hands free.

The term "boat level" is the older UK trade name. ITS.co.uk and some merchant catalogues still file torpedoes under "boat levels". The tool is identical.

When you actually need one

A torpedo is the right tool for short runs, tight spaces, and anything you need to check one-handed. It's the wrong tool for anything longer than about 400mm.

The use cases that come up repeatedly on a UK extension or renovation build:

• First-fix electrics. Levelling back boxes in stud walls, plumbing in conduit drops, aligning consumer unit brackets. A 600mm level won't fit in the bay between studs at 400mm centres. The torpedo does.
• First-fix plumbing. Checking the fall on short runs of waste pipe inside joist voids, setting the gradient on a shower trap before the screed goes down, levelling pipe clips. For the 1:40 fall on a soil pipe, a torpedo with a magnetic base clips to the pipe and reads the bubble position directly.
• Second-fix wall accessories. Radiator brackets, towel rails, TV brackets, cabinet brackets in wall units. Anywhere a full-size level is overkill or won't sit flat.
• Kitchen fitting. Levelling wall cabinet mounting rails in tight corners, aligning extractor cut-outs, checking appliance housing alignment where the 600mm level bumps the adjacent unit.
• Tile setting. Checking that a horizontal guide batten on a wall is level before tiling starts. The batten is the reference line every tile follows. Get it wrong and the whole wall goes wrong.

What a torpedo is not for: long wall runs, blockwork courses, door frames, worktop alignment, floor flatness. Anything over 400mm wants a 600mm level at minimum. This is the single most common beginner mistake with torpedoes. A 230mm level telling you a 2-metre wall is plumb is telling you nothing useful, because a gentle bow across that distance is invisible to a level that only reads the 230mm it's actually touching.

Magnetic or non-magnetic

Trade use is overwhelmingly magnetic. Every current mid-range and premium torpedo aimed at electricians and plumbers has rare-earth magnets in the base. The reasoning is practical: you can't hold a level against a vertical back box and also turn a screwdriver, and you can't steady a level on a copper pipe while you're shimming it with the other hand. Magnets free up a hand.

The current UK retail picture is split roughly like this:

• Magnetic: Magnusson 225mm, Stanley basic 230mm, Stanley FatMax Pro 250mm, Erbauer 255mm, OX Pro 230mm, Stabila 70TM and 70TMW, Stabila 81SM (premium die-cast), DEWALT Billet 165mm, Milwaukee Billet 170mm, Toughbuilt 230mm.
• Non-magnetic: Wickes own-brand 230mm, Stabila 70T 250mm, Stabila 81S 250mm (the non-magnetic version of the 81SM).

The Wickes own-brand is the main non-magnetic option for homeowners. The Stabila non-magnetic versions exist because some tradespeople specifically don't want magnets near instruments or because they're working on non-ferrous surfaces where magnets don't help. For a homeowner managing a build, buy magnetic. There's no practical downside and substantial upside.

Most trade magnetic torpedo levels are also classified as magnetic spirit levels, the compact form of the same tool. The magnetic spirit level guide covers rare-earth magnets, pull strength, and when magnetic matters on longer levels in detail.

The 45° vial problem

Most budget and mid-range torpedo levels have three vials: horizontal, plumb, and 45°. That third vial looks useful. It isn't, most of the time.

Stabila has made the calibration point explicit. The premium Stabila 70T, 70TM, 81S, and 81SM models deliberately omit the 45° vial. Stabila's view is that they only fit vials they can guarantee across the product's lifetime, and the 45° isn't one they'll stand behind. Budget and mid-range brands (Magnusson, Stanley, Erbauer, OX) include it because customers expect three vials on a torpedo and the manufacturing cost of adding a third vial is trivial.

This doesn't mean a three-vial torpedo is a bad tool. The horizontal and plumb vials on a Stanley FatMax Pro or an Erbauer are fine for trade use. It means the 45° on that tool is a convenience feature, not a precision instrument. Knowing that saves you from trusting a reading that shouldn't be trusted.

Body materials and accuracy

Three body constructions turn up on UK torpedo levels. They give you a useful price-to-accuracy split.

"0.5mm/m" means that across a 1-metre distance, the reading could be half a millimetre off true level. For the short runs a torpedo handles (typically 200mm to 400mm), that's a worst-case error of 0.1 to 0.2mm. Invisible to the eye and irrelevant for back boxes, brackets, and short pipe runs.

The 1.0mm/m accuracy on ABS plastic budget torpedoes is half as accurate. Still acceptable for hanging a shelf or levelling a picture frame. Not acceptable for checking pipe falls or first-fix accuracy where small errors compound across a long run.

The die-cast aluminium format (the Stabila 81S / 81SM trapezoidal body, or the short Milwaukee and DEWALT billet levels) adds rigidity that matters over time, not accuracy that matters on day one. A die-cast body doesn't flex under grip pressure, doesn't dent against steel edges, and keeps its vial alignment through years of being thrown into a tool bag.

The flip test: do this before you trust any new level

Every new spirit level, including every torpedo, must pass the flip test before you use it on anything that matters. This is the single most skipped step in DIY and the single biggest source of silent measurement errors.

1. Set the level on a roughly flat surface

   A kitchen worktop or a shelf works fine. The surface doesn't need to be perfectly level. You're testing the tool, not the surface.

2. Mark the position and note the bubble

   Put a pencil mark at each end of the level so you can replace it exactly. Look at the horizontal vial from directly above. Note exactly where the bubble sits relative to the two reference lines. Take a phone photo if it helps.

3. Rotate 180° end-for-end on the same marks

   Swap the left end to the right, keeping the level flat and on the same pencil marks. Don't flip it upside down. Rotate it horizontally in the plane of the surface.

4. Check the bubble position is identical

   If the bubble sits in exactly the same position as before, the horizontal vial is accurate. If it's shifted, the level is off. The actual inaccuracy is half the shift you see. Return the level or mark the accurate end.

Repeat the same test vertically for the plumb vial: hold the torpedo against a wall, note the bubble, then flip top-for-bottom without moving the position.

The flip test is covered in full on the parent spirit level page, with a step-by-step figure.

What to buy

Current UK retail pricing for torpedo levels sits in three clear tiers. Prices below from Screwfix, Toolstation, Wickes, and ITS, April 2026.

Click to enlarge

Budget tier (£5 – £12). Magnusson 225mm magnetic at Screwfix is the value pick at £7, with 0.5mm/m accuracy, rare-earth magnets, and a V-groove base. Stanley's basic 230mm magnetic at £9 is another reliable entry-level option. The Wickes own-brand 230mm at £5 is non-magnetic but genuinely fine for occasional use. Avoid the no-brand ABS plastic options at £3 – £5 unless you only need one for a picture frame.

Mid-range tier (£13 – £20). This is the sweet spot for a homeowner managing a build. OX Pro 230mm magnetic (Screwfix £16, ITS £13 on sale), Erbauer 255mm magnetic (Screwfix £15 with a lifetime guarantee), and Stanley FatMax Pro 250mm magnetic (Toolstation £15, Wickes £18) are all solid aluminium box-section torpedoes with 0.5mm/m accuracy and rare-earth magnets. The Stabila 70T non-magnetic 250mm (£14 Screwfix, £14 Wickes) and Stabila 70TM magnetic (£20 Screwfix) are two-vial trade levels with a ten-year guarantee.

Professional tier (£26 – £50). The Stabila 81S non-magnetic die-cast at Screwfix is £49. The Stabila 81SM magnetic die-cast with belt holster is £36 at ITS. Both have the distinctive trapezoidal body profile, two-vial layout (no 45°), 0.5mm/m accuracy, and lifetime calibration guarantees. The DEWALT Billet 165mm (£26) and Milwaukee Billet 170mm (£31) are the short-format premium alternatives, with amplified rare-earth magnets and machined billet bodies. Electricians who want a level that clips inside a consumer unit typically buy billet-format.

The set argument: why a standalone torpedo is often the wrong purchase

This is the part most torpedo articles skip. If you don't already own a 600mm and a 1200mm level, a standalone torpedo is probably the wrong first purchase.

A torpedo's use case is tight spaces and short runs. Every serious levelling job on an extension or renovation needs something longer as well. Checking a row of wall cabinets, a blockwork course, a door frame, a worktop, a radiator position against the wall below it: all of these need a 600mm level at minimum. A torpedo on its own can't do them.

UK merchants sell 3- and 4-piece spirit level sets that bundle a torpedo with a 600mm, 1200mm, and sometimes 1800mm level. The pricing is close enough to a standalone mid-range torpedo that it's almost always the better buy for someone starting out.

At £30–50, the Screwfix Essentials 4-piece covers every length a homeowner PM will need on an extension plus the torpedo. Buying the components separately in equivalent mid-range quality would cost twice that easily. The set is the honest recommendation for almost everyone reading this page.

Buy a standalone torpedo if you already own full-size levels and specifically need a compact one for pipework, back boxes, or cabinet brackets. Otherwise start with a set.

Alternatives and siblings

A torpedo is one member of a family of levelling tools. The siblings solve different problems.

A full-size spirit level in 600mm, 1200mm, or 1800mm is the right tool for anything over 400mm. No torpedo reads a long surface accurately.

A magnetic spirit level covers the broader family of levels with magnetic bases, including longer magnetic box-section levels used on steel beam installation and structural work. Most magnetic torpedoes are members of this family too.

A digital spirit level displays the angle on a screen to 0.1° or better, and can beep when it hits true level. Useful for setting pipe falls to a specific gradient (checking 1:40 against a read-out rather than guessing the 45° vial). Overkill for most torpedo work, but has its place on a plumber's van.

For one-off 45° checks where accuracy matters, a combination square or a protractor head is a better tool than the 45° vial on any torpedo.

Where you'll need this

Torpedo levels earn their place in a homeowner's tool kit during first fix and second fix. The tight-space jobs below are where a full-size level physically won't fit.

• First fix electrics: levelling back boxes, consumer unit mounting, conduit drops
• First fix plumbing: checking pipe falls in joist voids, levelling traps and clips
• Kitchen installation: aligning wall cabinet mounting rails, extractor cut-outs
• Tiling: checking horizontal guide battens before tile setting begins
• Second fix electrics: levelling accessory plates, switch and socket faces

These tasks appear across almost every extension, loft conversion, and renovation project. The torpedo format sits alongside a 600mm and 1200mm level as a standard hand tool for any homeowner doing their own first or second fix, or checking a trade's work.

The short version

If you already own a 600mm and a 1200mm level, add a mid-range magnetic torpedo for £13 – £20. The Erbauer, OX Pro, or Stanley FatMax Pro are all fine.

If you don't own any levels yet, buy the Screwfix Essentials 4-piece set for £30–50 and accept the torpedo in that set as good enough. You'll cover every length on your build for the price of one mid-range standalone level.

Flip-test every vial before you trust it. Don't trust the 45° vial on any torpedo that includes one. Don't use a torpedo for anything over 400mm. Keep the magnetic base clean, and the tool will last years.