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A standard reference material (SRM) is a certified reference material whose certified values are issued by NIST. It comes with a certificate stating each certified value, its uncertainty and its metrological traceability, and a lab uses it to calibrate or check a measurement. Reference material (RM), certified reference material (CRM) and SRM are nested terms, not synonyms.
Definition and scope
The National Institute of Standards and Technology (NIST) says it certifies and provides more than 1,200 Standard Reference Materials, each with a well-characterized composition or properties, or both (NIST SRM page). NIST’s own definitions page sets out three nested terms:
| Term | NIST definition |
|---|---|
| Reference material (RM) | Material, sufficiently homogeneous and stable with respect to one or more specified properties, which has been established to be fit for its intended use in a measurement process. |
| Certified reference material (CRM) | Reference material characterized by a metrologically valid procedure for one or more specified properties, accompanied by a certificate that provides the value of the specified property, its associated uncertainty, and a statement of metrological traceability. |
| NIST Standard Reference Material (SRM) | NIST CRMs that deliver values certified by NIST. |
So every SRM is a CRM and every CRM is an RM, but not the reverse. A CRM from another producer is not an SRM, and an RM without a certificate is not a CRM. NIST requires that every SRM delivers at least one certified value that is metrologically traceable to an internationally recognized higher-order reference system, such as the SI (NIST SRM definitions page).
How a standard reference material is used in practice
NIST lists the uses of its reference materials as calibrating measurement systems, assessing measurement procedures, assigning values to other materials, and quality control. In a lab this usually means a material of known, certified composition is measured alongside samples, and the result is compared with the certificate. For the wider idea of tying instrument readings to a reference, see our guide to what calibration is, and for an instrument-level example, spectrophotometer wavelength and photometric accuracy checks.
One rule from NIST’s definitions page is easy to miss: a single RM cannot be used for both calibration and validation of results in the same measurement procedure. If the same material sets the calibration and then judges the result, the check is not independent, so a lab needs a second, separate material for the validation step.
Reading the certificate: certified values and other values
The certificate, not the bottle label, carries the information that makes an SRM useful. NIST distinguishes two documents by what was certified:
- Certificate: issued for an SRM certified for one or more specific physical or engineering performance properties.
- Certificate of Analysis: issued for an SRM certified for one or more specific chemical properties.
A certified value is the value reported on an SRM certificate or certificate of analysis, the one for which NIST has the highest confidence in its accuracy. NIST also publishes non-certified values, a best estimate of the true value from currently available information. From 1987 until July 2020 NIST called these “reference values” when a potentially incomplete uncertainty estimate was attached, and “information values” when no uncertainty was given.
| Kind of value | What NIST says about it |
|---|---|
| Certified value | Reported on the certificate or certificate of analysis; NIST has the highest confidence in its accuracy; traceable to a higher-order reference such as the SI. |
| Non-certified value (historically “reference value”) | A best estimate of the true value; the older term applied where a potentially incomplete uncertainty estimate came with it. |
| Non-certified value (historically “information value”) | The older term applied to values without any associated uncertainty. |
Certificates may also state a period of validity where appropriate (NIST definitions page).
Where it matters for labs and supply decisions
Because the certificate defines what the material is certified for, a certificate check belongs in any receiving or method-validation routine. This checklist uses only points from NIST’s pages:
- Is it the right document type: a certificate for physical or engineering properties, or a certificate of analysis for chemical ones?
- Does it list the certified values you will actually use, with their uncertainties and the traceability statement?
- Is any period of validity still running?
- Is the certificate current? NIST states that users of a NIST SRM or RM should ensure the certificate or report in their possession is current, and says current certificates, reports of investigation and safety data sheets are found through NIST Store product search.
- Is the same material being asked to both calibrate and validate the same procedure? If so, it needs a second material.
For how an accredited lab’s own calibration certificates are read, see ISO/IEC 17025 calibration certificate interpretation. For the standard behind reference material producers, see our ISO 17034 guide. For a worked case of standardizing a solution against a reference, see gravimetric titration.
Common misunderstandings
- “Any certified reference material is an SRM.” Per NIST, an SRM is specifically a CRM whose values are certified by NIST.
- “An RM is as good as a CRM.” An RM need only be sufficiently homogeneous, stable and fit for its use; a CRM adds a certificate with value, uncertainty and traceability.
- “A certificate is valid forever.” NIST tells users to confirm the certificate in their possession is current, and certificates may carry a period of validity.
- “One material can do both jobs.” Not for the same measurement procedure: calibration and validation need separate materials.
FAQ
What is a standard reference material?
A NIST CRM, meaning a reference material with a certificate giving certified values, uncertainty and traceability, where NIST certified the values.
What is the difference between an SRM and a CRM?
A CRM is any reference material accompanied by such a certificate. An SRM is a CRM whose values are certified by NIST.
Can one reference material be used to both calibrate and validate?
Not in the same measurement procedure. NIST states that a single RM cannot be used for both calibration and validation of results in the same measurement procedure.
Where do I find the current certificate for an SRM?
NIST says current certificates, reports of investigation and safety data sheets are found via NIST Store product search.
Sources
- NIST, Standard Reference Materials. Checked 2026-10-29.
- NIST, SRM definitions. Checked 2026-10-29.
