Not supported in Google Sheets: Sheets can’t apply the number formats that keep U’s trailing zeros<\/li>\n<\/ul>\n <\/p>\n
Built by a calibration lab manager<\/h2>\n
Rick Hogan built and maintains this calculator. He managed an A2LA-accredited calibration lab for 14 years, served 6 years in US Navy metrology, and serves on A2LA’s Measurement Advisory Committee. Through ISOBudgets, he has helped hundreds of accredited labs calculate measurement uncertainty since 2011.<\/p>\n
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Frequently asked questions<\/h2>\nHow do I calculate calibration uncertainty for a calibration certificate?<\/h3>\n
Combine the CMC uncertainty from your scope of accreditation with the UUT’s resolution and repeatability by root sum of squares, then multiply by a coverage factor for about 95 % coverage. TECH-1-009 (formerly ILAC P14) requires these UUT contributions on the certificate. The calculator does every step for up to 1,000 results.<\/p>\n
Does the calculator meet ILAC P14 and TECH-1-009?<\/h3>\n
Yes. Global ACI TECH-1-009 carries over ILAC P14’s clauses, and the calculator follows them: it includes the UUT contributions, reports U with k at about 95 % coverage, rounds to two significant digits (5.3) and never reports less than the CMC (5.5).<\/p>\n
Can the uncertainty on a certificate be smaller than my CMC?<\/h3>\n
No. TECH-1-009 5.5 says accredited labs shall not report a smaller uncertainty than the CMC. The calculator rounds U conventionally and rounds up only when rounding would put it below the CMC.<\/p>\n
What does the calculator use for repeatability when all readings agree?<\/h3>\n
It uses the UUT resolution, d\/\u221a12, per JCGM 100:2008 F.2.2.1. It does the same when ur\/\u221an is smaller than d\/\u221a12 or when only one reading is taken.<\/p>\n
Can I enter a standard deviation from my R&R study for single readings?<\/h3>\n
No. Repeatability must come from the readings in the calibration you are reporting, with \u03bd = n \u2212 1: a single reading has n = 1, and the mean of 5 readings has n = 5 and \u03bd = 4. Your R&R variability is already in the CMC, so reusing it would count it twice.<\/p>\n
What is the difference between the Analog and Digital sheets?<\/h3>\n
On the Analog sheet, you enter resolution as the increment you read to, such as 0.5 psi. On the Digital sheet, you enter the number of digits to the right of the decimal, such as 2 for 12.34. Use the Analog sheet for any display that counts by 2 or 5.<\/p>\n
Which versions of Excel does it work in?<\/h3>\n
It works in Microsoft Excel 2010 or later on Windows and Mac, and in LibreOffice Calc. It is not supported in Google Sheets.<\/p>\n
Can I see and change the formulas?<\/h3>\n
Yes. Every formula is visible, and the Instructions sheet cites the reference for each calculation. Formula cells are protected without a password to prevent accidental changes; choose Review > Unprotect Sheet to edit them.<\/p>\n
How do I know the calculator is accurate?<\/h3>\n
The Validation sheet runs 18 test cases with independently calculated expected results and shows PASS for each. It covers normal results, low degrees of freedom, the CMC floor, small values and every input error message. You can keep it as software validation evidence for ISO\/IEC 17025:2017 7.11.2.<\/p>\n
Get the Calibration Uncertainty Calculator and report certificate uncertainties that hold up to assessment.<\/strong><\/p>\n