(832) 934 4140 info@calcgen.com 2500 Wilcrest Dr # 300 Houston, TX 77042

Bolt Torque Calculator
for Flange Bolting

Bolt diameter
1/4 inch and larger
(Thread major diameter in inches and decimals)
Bolt Dia.

Bolt lubricant or coating friction coefficient
This information is generally supplied by lubricant manufacturer
API Recognizes:
Enter 0.13 for uncoated bolts using API RP 5A3 / ISO 13678 thread compound OR
0.07 for Fluoropolymer (Teflon, Xylan, or SermaGard) coating.
Coefficient of Friction
Bolt Yeild Strength
105000 for ASTM A193 Gr. B7 or ASTM A320 Gr. L7 standard bolting
95000 for ASTM A193 Gr. B7 bolts larger than 2.5"
80000 for ASTM A193 Gr. B7M or ASTM A320 Gr. L7M Modified bolting up to 4"
Bolt Yield Strength

Bolt Yield Strength
50% specified by API 6A.
70% specified by API 17D.
Percent Yield


Note: This tool does not account for all possible combinations of loading. An engineering judgement is needed to use this number in design.

Values presented on SI Units are hard conversion of the results, so these values may not match exactly with the published values of API 6A