Dr. Nadia Petrov, PhD
Physicist & Metrologist
Bridging fundamental metrology and everyday measurement so every conversion carries the precision its context demands.
Dr. Nadia Petrov is a physicist and metrologist at the Bureau International des Poids et Mesures in Geneva, where she has spent over a decade working on the practical implementation of the International System of Units (SI). Her core research concerns the propagation of measurement uncertainty from primary national standards down to applied conversion contexts, the chain of traceability that determines whether a quoted value in joules, pascals, or knots can actually be trusted at the point of use. She contributed technical analysis to the 2019 SI redefinition project, which anchored base units to fixed numerical values of fundamental constants, and she continues to advise ISO/TC 12 on the documentary standards governing how quantities and units are expressed across scientific and commercial domains.
In applied work, Dr. Petrov has led uncertainty budget analyses for calibration laboratories across Europe and has co-authored guidance documents on unit conversion rounding, significant-figure conventions, and the correct handling of non-SI units still in widespread legal or industrial use, from nautical miles and barrels to electron volts and kilogram-force. She is particularly recognized for her methodical treatment of edge cases: unit systems with conflicting historical definitions, conversions that require temperature-dependent or pressure-dependent corrections, and the subtle errors that compound when intermediate rounding is applied at the wrong stage of a multi-step conversion. This expertise directly informs the calculators she authors and reviews for OnlyCalculators, where conversion logic is traced back to BIPM and NIST reference values rather than secondary sources.
At OnlyCalculators, Dr. Petrov oversees tools in the measurement, unit conversion, and metrology categories, reviewing both the underlying formulae and the explanatory content that surrounds them. Her standard for a published calculator is that a working scientist or engineer, not just a general audience, should be able to verify the method independently. She holds a fellowship from the Institute of Measurement and Control and holds ISO/IEC 17025 lead assessor accreditation through the Swiss Accreditation Service.
“Every calculator she publishes is anchored to a primary reference, BIPM, NIST, or a ratified ISO standard, so that the number a user reads carries the same traceability as a result from a calibrated laboratory.”