Thread Effective Stress Area Table

Complete Guide to Thread Tensile Stress Areas

Covering Metric (ISO/GB) and Imperial (Unified Inch) Fasteners

At Ever Power, we understand that the diameter of a bolt is not the only factor defining its strength. To accurately calculate the load-bearing capacity of a fastener, engineers must look beyond the nominal diameter and focus on the Tensile Stress Area. This represents the effective cross-sectional area of the threaded portion of a fastener that resists fracture under tensile load.

The following tables and formulas are based on GB/T 16823.1-1997 and international equivalents (ISO 898-1, ASME B1.1), providing the critical data needed for safety calculations in structural engineering.

1. Metric Thread Stress Areas ($mm^2$)

For Metric ISO threads, the stress area is calculated based on the mean of the pitch diameter ($d_2$) and the minor diameter ($d_3$). This table covers standard coarse and fine pitches from M1 to M48.

Thread Size Pitch (P)
mm		 Stress Area ($A_s$)
$mm^2$		 Thread Size Pitch (P)
mm		 Stress Area ($A_s$)
$mm^2$		 Thread Size Pitch (P)
mm		 Stress Area ($A_s$)
$mm^2$
M1 0.25 0.46 M12 1.75 84.27 M36 2 914.54
M1 0.2 0.52 M12 1.5 88.13 M36 1.5 939.85
M1.1 0.25 0.59 M12 1.25 92.07 M39 4 975.76
M1.1 0.2 0.65 M12 1 96.10 M39 3 1028.39
M1.2 0.25 0.73 M14 2 115.44 M39 2 1082.41
M1.2 0.2 0.80 M14 1.5 124.55 M39 1.5 1109.94
M1.4 0.3 0.98 M14 1 134.00 M42 4.5 1120.92
M1.4 0.2 1.15 M16 2 156.67 M42 4 1148.93
M1.6 0.35 1.27 M16 1.5 167.25 M42 3 1205.98
M1.6 0.2 1.57 M16 1 178.17 M42 2 1264.42
M2 0.4 2.07 M18 2.5 192.47 M45 4.5 1306.01
M2 0.25 2.45 M18 2 204.18 M45 4 1336.23
M2.5 0.45 3.39 M18 1.5 216.24 M45 3 1397.71
M3 0.5 5.03 M20 2.5 244.80 M48 5 1473.16
M4 0.7 8.78 M20 1.5 271.50 M48 3 1603.57
M5 0.8 14.18 M22 2.5 303.40 M52 5 1757.84
M6 1 20.12 M24 3 352.51 M56 5.5 2030.00
M8 1.25 36.61 M27 3 459.41 M64 6 2676.00
M10 1.5 57.99 M30 3.5 560.59 M70 6 3254.39

Metric Formula (GB/T 16823.1 / ISO 898-1)

As = (π / 4) * [ (d2 + d3) / 2 ]²

  • $d_2$: Basic Pitch Diameter
  • $d_3$: Minor Diameter at Root ($d_3 = d_1 – H/6$)
  • H: Fundamental Triangle Height

2. Imperial (Unified) Thread Stress Areas

For Unified Inch threads (UNC, UNF), the calculation uses the nominal diameter and the number of threads per inch ($n$). This is standard for ASME/ANSI B1.1 fasteners.

Size Diameter
(in)		 TPI
(n)		 Stress Area ($A_s$)
$in^2$		 Size Diameter
(in)		 TPI
(n)		 Stress Area ($A_s$)
$in^2$
1# 0.073 64 0.00262 1/4″ 0.250 20 0.0318
2# 0.086 56 0.00370 5/16″ 0.3125 18 0.0524
3# 0.099 48 0.00486 3/8″ 0.375 16 0.0775
4# 0.112 40 0.00603 7/16″ 0.4375 14 0.1063
5# 0.125 40 0.00796 1/2″ 0.500 13 0.1419
6# 0.138 32 0.00909 5/8″ 0.625 11 0.2260
8# 0.164 32 0.0140 3/4″ 0.750 10 0.3345
10# 0.190 24 0.0175 1″ 1.000 8 0.6057

Imperial Formula (ASME B1.1)

As = 0.7854 * ( D – 0.9743 / n )²

  • D: Nominal Diameter (inches)
  • n: Number of threads per inch (TP

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