Customizable cover page
Add your logo, state the reason for the comparison, record the date, and identify both laboratories. The cover page turns a worksheet into a report your document control system can hold.
Interlaboratory Comparison En Calculator - Free Download
Free Excel Template
Interlaboratory Comparison Template With a Built In En Calculator
No proficiency testing scheme covers your measurement, and your assessor still wants evidence that your results hold up. This interlaboratory comparison template turns two sets of results into a single pass or fail decision. Enter both laboratories' values and expanded uncertainties, and the workbook calculates the normalized error at every point.
- Supports ISO/IEC 17025:2017 clause 7.7
- Acceptance rule |En| ≤ 1
- Microsoft Excel (.xlsx)
- Free to download
Tell us where to send it, and the download appears right after you submit the form.
What Is Inside the Interlaboratory Comparison Template
The workbook holds the two documents an assessor expects to see: a cover page that explains why you ran the comparison, and a data page that shows the arithmetic behind your conclusion.
Shared point data entry
Line up both laboratories side by side, matched by nominal value. Each row carries the two results and the two expanded uncertainties for one measurement point.
En calculated at every point
The normalized error formula sits in the sheet. Enter the four inputs for a point, and the workbook returns the En value without a side calculation.
Pass or fail at a glance
Each point reports against the |En| ≤ 1 rule, so a reviewer sees the outcome without interpreting the number. Failures stand out for investigation instead of hiding in a column.
Coverage factor on the record
Capture the coverage factor each laboratory used. Mixing a k = 2 uncertainty with a k = 1 uncertainty distorts the comparison, so the sheet keeps that detail visible.
A report you can hand over
Print the cover page and the data summary, attach both calibration certificates, and the evidence package is complete. Assessors follow it without asking you to fill gaps.
En =
x1 − x2
√(U12 + U22)
The statistic the workbook calculates
- x1, x2
- The two laboratories' results at the same measurement point.
- U1, U2
- The expanded uncertainty each laboratory reports at that point.
The numerator holds the raw difference. The denominator holds the difference the combined uncertainty already allows. A point passes when the absolute value of En stays at 1 or below.
How to Run the Comparison
The sequence holds across measurement disciplines. Work through it in order, because the first step protects everything after it.
-
Get the plan approved
Accreditation bodies generally expect proficiency testing first. State your reason and secure approval before you rely on a comparison.
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Choose the item
Pick a device or sample with a current certificate or reported result from an accredited laboratory, covering the points in your scope.
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Measure it yourself
Run your own calibration or test on that item. Capture data at each nominal point you plan to compare.
-
Match points and uncertainties
Enter both readings by nominal value, record each expanded uncertainty, and confirm both laboratories report at the same coverage factor.
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Read the En values
Check every matched point against the |En| ≤ 1 rule. Investigate and document any point that fails rather than repeating the measurement until it passes.
-
Assemble the package
Combine the cover page, the data summary, and both certificates into one report, and file it with your validity monitoring records.
Get the Interlaboratory Comparison Template
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- Free, no payment required
- Editable Excel workbook
- Yours to rebrand and reuse
Download the Excel File
This excel file will help you do the following:
- create a method verification report for auditors
- populate a cover sheet (customizable with our own logo)
- run an interlaboratory comparison
- calculate the En values
- check if your measurement data is compliant with the En values
What a Completed Comparison Looks Like
Two laboratories received portions of the same water sample and determined three analytes by ion chromatography. Both reported results in milligrams per liter with expanded uncertainties on the same coverage basis.
| Analyte | Lab 1 result | Lab 1 U | Lab 2 result | Lab 2 U | Difference | Combined U | En | Evaluation |
|---|---|---|---|---|---|---|---|---|
| Fluoride | 1.02 | 0.06 | 0.99 | 0.05 | 0.03 | 0.078 | 0.38 | Satisfactory |
| Chloride | 25.4 | 0.80 | 25.0 | 0.70 | 0.40 | 1.063 | 0.38 | Satisfactory |
| Bromide | 0.48 | 0.04 | 0.50 | 0.05 | −0.02 | 0.064 | −0.31 | Satisfactory |
Every point sits well inside the acceptance rule, so the comparison supports the method. Calibration laboratories use the same layout, with nominal load points in place of analytes.
Who Uses This Template
The workbook fits any laboratory that has to show its results agree with someone else's. Use it for a single new parameter or across a whole scope.
Labs with no suitable PT scheme
No provider covers your measurement, or the available scheme stops short of your range. A comparison gives you evidence that meets the same requirement.
Labs adding a parameter
You expanded your scope and the next proficiency testing round sits months away. Use a comparison for interim verification, and document it properly.
Quality managers building evidence
You need the calculation, the decision, and the certificates in one package. The workbook gives you a layout you can reuse for every verification.
Interlaboratory Comparison FAQ
Does an interlaboratory comparison satisfy ISO 17025?
ISO/IEC 17025:2017 clause 7.7 asks you to monitor the validity of your results. It points to comparison with other laboratories where that comparison is available and appropriate. Proficiency testing is the common route, and an interlaboratory comparison serves the same purpose when a scheme does not fit.
Accreditation bodies generally expect proficiency testing as the first course of action. State your reason, and get your monitoring plan approved before you rely on a comparison. Verify clause references against your controlled copy of the standard.
What En value counts as a pass?
A point passes when the absolute value of En stays at 1 or below. The statistic divides the difference between the two results by their combined expanded uncertainty. A value at or under 1 means the gap sits inside the uncertainty both laboratories already declared.
The normalized error is the accepted agreement statistic for proficiency testing and comparison work. Its formal definition sits in the statistical standards for those programs. Confirm the exact definition and any coverage factor requirement before you rely on it.
What if the two laboratories report at different coverage factors?
Standardize before you compare. Mixing a k = 2 uncertainty with a k = 1 uncertainty distorts the result. The denominator no longer represents the same confidence on both sides. When the other laboratory uses a different coverage factor, expand your own uncertainty to match it, and record the factor you used.
Can testing laboratories use this, or is it only for calibration?
Both. A calibration laboratory compares readings on a shared artifact at matched nominal points. A testing laboratory analyzes portions of the same sample and compares reported results for each analyte. The arithmetic does not change, and the workbook handles either layout.
What do I do when a point fails?
Investigate it. A failed point is data, not a formatting problem, so do not repeat the measurement until it passes. Run it through your nonconforming work process and your corrective action process, and record what you found and what you changed. A poor result handled well demonstrates a functioning management system.
Does this replace proficiency testing?
No. Treat the comparison as the option you use when proficiency testing is unavailable, out of range, or disproportionate to the verification. Your accreditation body sets the expectations for your monitoring program, and those expectations usually put proficiency testing first.
Where do the uncertainties come from?
Your side comes from your own uncertainty budget for the method, and the other laboratory's comes from its certificate or report. If you have not built a budget for the method yet, start there. The En calculation only carries as much weight as the uncertainty estimates behind it.
Use the Template With These Resources
The comparison depends on sound uncertainty estimates. These resources cover the work that feeds it.
Uncertainty Budget Excel Template
Build the expanded uncertainty you enter on your side of the comparison, with a cover sheet, Type A data, and a contributor table.
Calculating Measurement Uncertainty
Four steps from measurand to expanded uncertainty, with a worked example and a column by column walk through the budget.
ISO 17025 Knowledge Base
Guides, technical articles, and templates for testing and calibration laboratories, updated as we publish.
Want a second set of eyes on your monitoring plan?
Precision ISO helps laboratories plan validity monitoring and build the uncertainty budgets the En calculation depends on. We also help assemble evidence packages that hold up during an assessment.
This template is a customizable starting point. Review and adapt it to your organization's scope, methods, and processes before use. It does not constitute legal, regulatory, or accreditation advice, and it guarantees no assessment outcome. Clause references point to ISO/IEC 17025:2017, clause 7.7, and uncertainty terms follow the GUM (JCGM 100:2008). Verify every clause reference, the normalized error definition, and any coverage factor requirement against your controlled copies of the standards.
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