Resistor characteristics are quantified and reported using various national standards. In the US, MIL-STD-202 contains the relevant test methods to which other standards refer.
There are various standards specifying properties of resistors for use in equipment:
IEC 60062 (IEC 62) / DIN 40825 / BS 1852 / IS 8186 / JIS C 5062 etc. (Resistor color code, letter and digit code, date code)
EIA RS-279 / DIN 41429 (Resistor color code)
IEC 60063 (IEC 63) / JIS C 5063 (Standard E series values)
MIL-PRF-39007 (Fixed power, established reliability)
MIL-PRF-55342 (Surface-mount thick and thin film)
MIL-R-11 STANDARD CANCELED
MIL-R-39017 (Fixed, General Purpose, Established Reliability)
MIL-PRF-32159 (zero ohm jumpers)
UL 1412 (fusing and temperature limited resistors)
There are other United States military procurement MIL-R- standards.
The primary standard for resistance, the "mercury ohm" was initially defined in 1884 in as a column of mercury 106.3 cm long and 1 square millimeter in cross-section, at 0 degrees Celsius. Difficulties in precisely measuring the physical constants to replicate this standard result in variations of as much as 30 ppm. From 1900 the mercury ohm was replaced with a precision machined plate of manganin. Since 1990 the international resistance standard has been based on the quantized Hall effect discovered by Klaus von Klitzing, for which he won the Nobel Prize in Physics in 1985.
Resistors of extremely high precision are manufactured for calibration and laboratory use. They may have four terminals, using one pair to carry an operating current and the other pair to measure the voltage drop; this eliminates errors caused by voltage drops across the lead resistances, because no charge flows through voltage sensing leads. It is important in small value resistors (100–0.0001 ohm) where lead resistance is significant or even comparable with respect to resistance standard value.