How To Calculate Uncertainty
Without Losing Your Mind
If you’re working in calibration, you’ve probably heard it a hundred times:
“What’s your uncertainty?”
“Did you include resolution?”
“Is that a rectangular or normal distribution?”
And you’ve probably also opened Excel, stared at a table of contributors, and wondered if any of this actually matters.
It does. But it doesn’t have to be complicated.
🔢 The Simple Steps to Calculate Uncertainty
Let’s say you’re calibrating a digital multimeter. Here’s what you need:
1. List All Contributors
Resolution
Repeatability
Standard’s uncertainty
Temperature effect
Operator variability (if applicable)
2. Convert Everything to Standard Uncertainty
For each contributor:
Divide by √3 if rectangular
Divide by √6 if triangular
Leave alone if normal
3. Combine Contributors
Use RSS:
uc=u12+u22+u32+…u_c = \sqrt{u_1^2 + u_2^2 + u_3^2 + \ldots}uc=u12+u22+u32+…
4. Apply Coverage Factor
Typically:
Use k = 2 for 95% confidence
Expanded Uncertainty = U=k⋅ucU = k \cdot u_cU=k⋅uc
✅ Now What?
Compare your reading ± expanded uncertainty to your tolerance spec. If the whole uncertainty band fits within the tolerance, it passes.
🛠️ But What If You Don’t Want to Do the Math?
That’s why I built QuickCheck—a free Windows tool that:
Takes your setpoint, reading, tolerance, and uncertainty
Instantly calculates error and expanded uncertainty
Shows PASS or FAIL in big clear text
No install, no bloat—just a standalone .exe that works.