What is a spirit level's tolerance?

Manufacturing tolerance is the sum of all possible minor and microscopically small errors during production. Tolerance is thus the divergence from sensitivity, and the smaller the value the better.

Hultafors spirit levels contains block vials

For the highest accuracy the finest spirit levels from Hultafors feature block vials. Hultafors block vials have a defined inner contour and are symmetrical around both the X- and Y-axis.

Tolerance for standard and reversed position

The tolerance of all vials used is calculated for both standard and reversed position. This allows for exact measuring both when measuring atop a surface, and from below.

How to measure from below

Remember, when measuring against a surface from below always to turn the spirit level upside down. This ensures that you always measure with the bottom surface of the spirit level, since it is this surface the vials are calibrated against.