The Density of Water as STP (Standard Temperature and Pressure) is 998.2071kg/m3. The Density of Water at STP is used as a reference substance for defining the Specific Gravity of many things (e.g. gems). The density of water at Standard Temperature and Pressure (STP) is 62.428 lbs/ft3 in English units
NIST uses a temperature of 20 C (293.15 K, 68 F) and an absolute pressure of 101.325 kPa (14.696 psi, 1 atm).
The International Standard Metric Conditions for natural gas and similar fluids are 288.15 K (59.00 F; 15.00 C) and 101.325 kPa.
In chemistry, IUPAC established standard temperature and pressure (informally abbreviated as STP) as a temperature of 273.15 K (0 C, 32 F) and an absolute pressure of 100 kPa (14.504 psi, 0.987 atm, 1 bar). An unofficial, but commonly used standard is standard ambient temperature and pressure (SATP) as a temperature of 298.15 K (25 C, 77 F) and an absolute pressure of 100 kPa (14.504 psi, 0.987 atm). The STP and the SATP should not be confused with the standard state commonly used in thermodynamic evaluations of the Gibbs energy of a reaction.