Real steam-table density and specific volume from the IAPWS Industrial Formulation 1997 — the same basis used for plant heat balances, not an ideal-gas approximation.
Verified against published standard
State Point
Pressure must be absolute. Gauge pressure + ~1.013 = absolute at sea level.
Saturation Lookup
Enter a state point.
About This Calculation
Steam behaves nothing like an ideal gas at the pressures used in real power plants — real molecular interactions and the proximity to the saturation curve mean an ideal-gas approximation can be off by 10% or more on density at typical main-steam conditions. IAPWS-IF97 is the industry-standard steam property formulation used by real plant heat balance software and steam tables; this calculator implements it directly (Regions 1, 2 and 4 — compressed liquid, superheated steam, and the saturation line) rather than approximating, because for flow measurement in particular, density error carries straight through into flow error.
Frequently Asked Questions
Why does ideal-gas density matter for flow measurement specifically?
DP flow measurement scales with the square root of density, so a density error of X% becomes roughly an X/2% flow error — at typical main-steam pressures (100–170 bar), ideal-gas density can be off by 8–11%, which is a genuinely significant flow error, not a rounding difference.
What steam conditions does this calculator NOT cover?
IAPWS-IF97 Region 3 (near-critical, above roughly 350°C at pressures approaching the critical point) is not implemented here — the calculator explicitly refuses those inputs rather than silently returning an inaccurate number.
Do I need gauge or absolute pressure?
Absolute pressure — gauge pressure plus roughly 1.013 bar (atmospheric) at sea level. Using gauge pressure directly into a steam property calculation is a common source of error, especially at lower pressures where the difference is proportionally larger.
How is steam density related to saturation temperature?
At a given pressure, there is exactly one saturation temperature; above it the steam is superheated (this calculator’s Region 2), below it you have subcooled water (Region 1). Right at saturation, density is extremely sensitive to small temperature changes — which is also why steam quality becomes uncertain and DP flow measurement gets unreliable near the saturation line.