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Certain features of Sigma-Aldrich.com will be down for maintenance the evening of Friday August 18th starting at 8:00 pm CDT until Saturday August 19th at 12:01 pm CDT.   Please note that you still have telephone and email access to our local offices. We apologize for any inconvenience.

Stable Isotopes

STP vs. NTP Gas Volume

ISOTEC® reports all gas volumes at Standard Temperature and Pressure (STP), while some suppliers quote their gas volumes at Normal Temperature and Pressure (NTP). One STP Liter is 7.7% more gas than one NTP Liter. Use this handy calculator to compare cost:

STP to NTP Cost Calculator
Enter Dollars per STP Liters
Enter Dollars per NTP Liters