Uncertainty Distribution Divisor (Rectangular, Triangular…)
Convert a ± half-width into a standard uncertainty using the divisor for rectangular, triangular, U-shaped or normal distributions.
Worked example
Input: Half-width a (± value) 1 dB, Distribution Rectangular (√3)
Result: Standard uncertainty u = a / divisor 0.57735 dB
Result: Standard uncertainty u = a / divisor 0.57735 dB
Formula
u = a / divisor
Rectangular √3, triangular √6, U-shaped √2, normal (95 %) 2
How it works
Calibration certificates and datasheets usually give limits of the form "±a". To combine them you divide by a distribution-dependent divisor to obtain a standard uncertainty. When only the limits are known and nothing else about the distribution, a rectangular distribution (√3) is the usual default, and mismatch uncertainty is conventionally treated as U-shaped (√2).
Practical tipFor a normal distribution quoted at "95 %" divide by 2, for "k=3" divide by 3. Picking the wrong distribution changes the divisor anywhere between 1 and 2.45, which can shift the standard uncertainty by tens of percent or more, so check the confidence level printed on the certificate.
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Results and summaries are for reference. For certification and test reports use the latest official standard text and calibrated instrument data. Last updated: 2026-10-10