Gurley Second (s/100 mL)
The Gurley second is the time, in seconds, for 100 mL of air to pass through 6.45 cm² (one square inch) of a sheet under a pressure difference of 1.22 kPa (TAPPI T 460, ISO 5636-5). It is an air resistance: the higher the number, the less porous the material. Battery separators, sack kraft, filter papers and membranes are specified in Gurley seconds.
Symbol: s/100 mL
Quantity: air permeance (air flow per unit area per unit pressure difference)
SI relation: Gurley t = seconds for 100 mL of air through 6.45 cm² at 1.22 kPa, so P = 100 mL ÷ (6.45 cm² × 1.22 kPa × t) ≈ 127.08 ÷ t µm/(Pa·s).
Derivation: Gurley t = seconds for 100 mL of air through 6.45 cm² at 1.22 kPa, so P = 100 mL ÷ (6.45 cm² × 1.22 kPa × t) ≈ 127.08 ÷ t µm/(Pa·s).
Exact: no, measured or rounded value
Reference conditions. 100 mL through 6.45 cm² (1 in²) at 1.22 kPa (TAPPI T 460, ISO 5636-5); assumes air flow proportional to pressure difference.
History
Named after the W. & L.E. Gurley company of Troy, New York, which built the densometer in the early 1900s.
Typical uses
- Paper, board and sack kraft porosity
- Lithium-ion battery separator air permeability
- Membranes, filter media and nonwovens
Convert Gurley seconds to other units
| Conversion | 1 s/100 mL equals | Reverse |
|---|---|---|
| Gurley second to micrometre per pascal second | 127.0809506 µm/(Pa·s) | micrometre per pascal second to Gurley second |
| Gurley second to Frazier | 3.126991894 cfm/ft² @125 Pa | Frazier to Gurley second |
| Gurley second to Bendtsen | 11208.53984 mL/min (Bendtsen) | Bendtsen to Gurley second |
| Gurley second to millimetre per second at 100 Pa | 12.70809506 mm/s @100 Pa | millimetre per second at 100 Pa to Gurley second |
| Gurley second to millimetre per second at 200 Pa | 25.41619011 mm/s @200 Pa | millimetre per second at 200 Pa to Gurley second |
Open the Gurley to Air Permeance Converter (Bendtsen, Frazier) to convert any value between all units.
Sources
- ISO 5636 Paper and board — Determination of air permeance (Part 3: Bendtsen method; Part 5: Gurley method), International Organization for Standardization , Part 5, Gurley method.
- TAPPI T 460 om-21 Air resistance of paper (Gurley method), TAPPI .
Last reviewed: . Factors are stored exactly and computed with 50-digit decimal arithmetic. See how we verify conversion factors.
Cite this page
APA
Scientific Converters. (2026, October 15). Gurley Second (s/100 mL). Retrieved October 29, 2026, from https://scientificconverters.com/units/gurley-second/
IEEE
Scientific Converters, "Gurley Second (s/100 mL)," scientificconverters.com. Accessed: Oct. 29, 2026. [Online]. Available: https://scientificconverters.com/units/gurley-second/