A spirit level is arguably the most fundamental tool in any DIYer’s kit — and the one most often used incorrectly. Getting a truly level or plumb surface is the foundation of every building, tiling, shelving, and fencing project. If the level is wrong, everything built on top of it will be wrong too.
Types of Spirit Level
| Type | Length | Best For | Price |
|---|---|---|---|
| Torpedo level | 200–250mm | Small tasks, plumbing, electrics, tight spaces | £5–£15 |
| Box level (standard) | 600–1200mm | General DIY, shelving, tiling, landscaping | £15–£50 |
| Long box level | 1800–2400mm | Stud walls, door frames, large installations | £30–£80 |
| Post level | Wraps around post | Fence posts, deck posts — checks plumb on two faces simultaneously | £5–£10 |
| Digital level | Various | Precise angle measurement, accessibility | £20–£60 |
| Laser level | Projects line across room | Tiling, kitchen fitting, picture hanging over long distances | £20–£200 |
For general DIY, a 600mm box level covers most jobs. A 1200mm level is better for anything structural — stud walls, door frames, kitchen units — because it spans a longer distance and averages out local bumps. If you only buy one, get a 1200mm from a reputable brand. Cheap levels lie to you — spend £20–£40 on a decent one from Stabila, Stanley FatMax, or Draper. Our laser level guide covers when to step up to a laser.
How to Read the Bubble Correctly
The vial (the tube with the bubble) is the heart of the level. It’s filled with a coloured liquid with a single air bubble. When the surface is level, the bubble sits exactly between the two marked lines on the vial.
The Three Vials
- Horizontal vial (centre of the level) — reads whether a surface is level (horizontal)
- Vertical vials (one at each end) — read whether a surface is plumb (vertical)
On a quality level, each vial has two lines. The bubble must sit exactly between these two lines for a true reading. If it’s touching either line or beyond them, the surface isn’t level. Some premium levels have magnified vials for easier reading — worth the extra cost if your eyesight isn’t perfect.
Is Your Spirit Level Accurate? (How to Check)
Before trusting your level, verify it’s accurate. Even quality levels can be knocked out of calibration:
Checking the Horizontal Vial
- Place the level on a flat surface (a kitchen worktop works)
- Note the exact position of the bubble
- Rotate the level 180° (swap left end for right end) and place it on the same spot
- If the bubble is in the same position in both orientations, the level is accurate
- If the bubble position changes, the level is out. Replace it — you can’t recalibrate most DIY levels
Checking the Vertical Vial
- Hold the level against a wall or door frame and note the bubble position
- Rotate the level 180° (flip it so the other face is against the wall) in the same position
- The bubble should read the same in both orientations
The Stabila accuracy check guide has detailed instructions with illustrations.
Common Mistakes
1. Dirty or Uneven Surfaces
A grain of sand or a blob of plaster under the level will give a false reading. Always clean the surface and the bottom edge of the level before checking. On rough surfaces (brick, stone), be aware that local bumps affect the reading — use the longest level practical to average out surface variations.
2. Parallax Error
Reading the bubble from an angle makes it appear to be in a different position than it actually is. Always read the vial from directly above or in front — perpendicular to the vial. If you’re up a ladder reading a level on a wall below, the angle makes the bubble appear off-centre even when it’s not.
3. Confusing Level with Flat
A level surface isn’t necessarily flat, and a flat surface isn’t necessarily level. Your kitchen worktop might be perfectly flat but not level (it could slope slightly). A spirit level checks level (relative to gravity) — use a straight edge to check flatness.
4. Temperature Effects
In extreme cold, the liquid in spirit level vials becomes more viscous and the bubble moves more slowly. In extreme heat, it becomes less viscous and the bubble is jittery. For critical work, let the level acclimatise to ambient temperature for 30 minutes.
5. Using Too Short a Level
A 200mm torpedo level on a 2-metre shelf span is practically useless — it only tells you that the 200mm section under the level is flat, not the entire shelf. Use the longest level that fits the job.
When to Use a Laser Level Instead
A spirit level works brilliantly for individual items — a single shelf, a row of tiles, a fence post. But for anything that spans a large area (a full wall of tiles, kitchen units across 3 metres, a picture rail around a room), a laser level is faster, easier, and more accurate. It projects a perfectly level line across the entire room, giving you a reference you can work to without constantly repositioning a spirit level.
Taking Care of Your Level
- Store it flat or hanging — don’t lean it against a wall where it can fall and knock the vials out of calibration
- Clean the edges after use — dried adhesive, plaster, or paint on the bottom edge causes false readings
- Don’t use it as a straight edge for cutting — a knife or saw will damage the edge
- Check calibration regularly — especially if it’s been dropped or knocked
