Skip to main content

Chemical Safety
Calculators
Time Weighted Average
Threshold Limit Values for Silica
TLV for Liquids
Minimum Sampling Volume
NIOSH PPM to mg/m3

Time Weighted Average Calculator

Use this formula to determine a person's time-weighted average (TWA) for exposure to a chemical. The total time (Tf) is the total time of exposure. Typically, this is assumed to be an 8-hour period to determine the compliance with OSHA PELs. However, the total time can be decreased to match the actual time of exposure, to calculate the worst-case scenario.

Concentration 1:
Time 1: Hours
Concentration 2:
Time 2: Hours
Concentration 3:
Time 3: Hours
Concentration 4:
Time 4: Hours
Concentration 5:
Time 5: Hours
Total Time Hours
Time Weighted Average: