Accuracy Rating
Affiliate link — we may earn a commissionAccuracy rating tells you how far off a measuring tool can be from the true value, expressed as a tolerance. A laser level rated at plus or minus 1/8-inch at 30 feet means the projected line could be up to 1/8-inch above or below true level at that distance. A tape measure rated Class 1 under EU standards is accurate to plus or minus 1.1 mm at 10 meters. Cheaper tools have wider tolerances. For rough framing, 1/4-inch tolerance at 30 feet is fine. For tile work or cabinetry, you need 1/16-inch or better.
Why It Matters
Tolerance compounds over distance. A level that's off by 1/8-inch at 30 feet is off by 1/2-inch at 120 feet. For a long interior wall or a concrete pour, that's the difference between level and visibly crooked.