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Wide Flange Steel I Beam: W18 × 40
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Glossary » Beams » Simply Supported » Uniformly Distributed Load » Three Equal Spans » Wide Flange Steel I Beam » W18 × 40
Wide Flange Steel I Beam | Single Span | Two Equal Spans | Three Equal Spans | Four Equal Spans

For a simply supported beam in three equal spans, we compute the displacement at the middle of the first and the third spans, and the maximum normal stress stress_max occuring at the second and third supports of the beam.
The tabulated data listed in this page are calculated based on the area moment of inertia (Ixx = 612 in4) for the W18 × 40 Wide Flange Steel I Beam and the typical Young's modulus (E = 3.046 × 107 psi) of steels. Note that the typical yielding stress Yield of steels can range from 1.015 × 104 to 2.970 × 105 psi. The purpose of this page is to give a rough estimation of the load-bearing capacity of this particular beam, rather than a guideline for designing actual building structures. Please check your local building codes for regulatory requirements.

Note: The weight of the beam itself is not included in the calculation.
L = 3 ft
L = 5 ft
L = 10 ft
L = 15 ft
L = 20 ft
L = 25 ft
L = 30 ft
L = 40 ft
L = 50 ft
L = 60 ft
L = 70 ft
L = 80 ft
L = 90 ft
L = 100 ft
L = 125 ft
L = 150 ft
   
Steel I Beam: W18 × 40 (Wide Flange 18 inch tall × 40 lbf/ft)
L = 3.00 ft
P (lbf/ft) w_max (in) stress_max (psi)
40.0 2.04 × 10-6 6.32
50.0 2.55 × 10-6 7.90
60.0 3.06 × 10-6 9.48
70.0 3.57 × 10-6 11.1
80.0 4.08 × 10-6 12.6
90.0 4.60 × 10-6 14.2
100 5.11 × 10-6 15.8
200 1.02 × 10-5 31.6
300 1.53 × 10-5 47.4
400 2.04 × 10-5 63.2
500 2.55 × 10-5 79.0
600 3.06 × 10-5 94.8
700 3.57 × 10-5 111
800 4.08 × 10-5 126
900 4.60 × 10-5 142
1000 5.11 × 10-5 158
2000 1.02 × 10-4 316
3000 1.53 × 10-4 474
4000 2.04 × 10-4 632
5000 2.55 × 10-4 790
6000 3.06 × 10-4 948
7000 3.57 × 10-4 1110
8000 4.08 × 10-4 1260
9000 4.60 × 10-4 1420
1.00 × 104 5.11 × 10-4 1580
2.00 × 104 0.00102 3160
3.00 × 104 0.00153 4740
4.00 × 104 0.00204 6320
5.00 × 104 0.00255 7900
6.00 × 104 0.00306 9480
7.00 × 104 0.00357 1.11 × 104
8.00 × 104 0.00408 1.26 × 104
9.00 × 104 0.00460 1.42 × 104
1.00 × 105 0.00511 1.58 × 104
2.00 × 105 0.0102 3.16 × 104
3.00 × 105 0.0153 4.74 × 104
4.00 × 105 0.0204 6.32 × 104
5.00 × 105 0.0255 7.90 × 104
6.00 × 105 0.0306 9.48 × 104
7.00 × 105 0.0357 1.11 × 105
8.00 × 105 0.0408 1.26 × 105
9.00 × 105 0.0460 1.42 × 105
1.00 × 106 0.0511 1.58 × 105
1.88 × 106 0.0960 2.97 × 105
Steel I Beam: W18 × 40 (Wide Flange 18 inch tall × 40 lbf/ft)
L = 5.00 ft
P (lbf/ft) w_max (in) stress_max (psi)
40.0 1.58 × 10-5 17.5
50.0 1.97 × 10-5 21.9
60.0 2.36 × 10-5 26.3
70.0 2.76 × 10-5 30.7
80.0 3.15 × 10-5 35.1
90.0 3.55 × 10-5 39.5
100 3.94 × 10-5 43.9
200 7.88 × 10-5 87.7
300 1.18 × 10-4 132
400 1.58 × 10-4 175
500 1.97 × 10-4 219
600 2.36 × 10-4 263
700 2.76 × 10-4 307
800 3.15 × 10-4 351
900 3.55 × 10-4 395
1000 3.94 × 10-4 439
2000 7.88 × 10-4 877
3000 0.00118 1320
4000 0.00158 1750
5000 0.00197 2190
6000 0.00236 2630
7000 0.00276 3070
8000 0.00315 3510
9000 0.00355 3950
1.00 × 104 0.00394 4390
2.00 × 104 0.00788 8770
3.00 × 104 0.0118 1.32 × 104
4.00 × 104 0.0158 1.75 × 104
5.00 × 104 0.0197 2.19 × 104
6.00 × 104 0.0236 2.63 × 104
7.00 × 104 0.0276 3.07 × 104
8.00 × 104 0.0315 3.51 × 104
9.00 × 104 0.0355 3.95 × 104
1.00 × 105 0.0394 4.39 × 104
2.00 × 105 0.0788 8.77 × 104
3.00 × 105 0.118 1.32 × 105
4.00 × 105 0.158 1.75 × 105
5.00 × 105 0.197 2.19 × 105
6.00 × 105 0.236 2.63 × 105
6.77 × 105 0.267 2.97 × 105
Steel I Beam: W18 × 40 (Wide Flange 18 inch tall × 40 lbf/ft)
L = 10.0 ft
P (lbf/ft) w_max (in) stress_max (psi)
40.0 2.52 × 10-4 70.2
50.0 3.15 × 10-4 87.7
60.0 3.78 × 10-4 105
70.0 4.41 × 10-4 123
80.0 5.04 × 10-4 140
90.0 5.67 × 10-4 158
100 6.30 × 10-4 175
200 0.00126 351
300 0.00189 526
400 0.00252 702
500 0.00315 877
600 0.00378 1050
700 0.00441 1230
800 0.00504 1400
900 0.00567 1580
1000 0.00630 1750
2000 0.0126 3510
3000 0.0189 5260
4000 0.0252 7020
5000 0.0315 8770
6000 0.0378 1.05 × 104
7000 0.0441 1.23 × 104
8000 0.0504 1.40 × 104
9000 0.0567 1.58 × 104
1.00 × 104 0.0630 1.75 × 104
2.00 × 104 0.126 3.51 × 104
3.00 × 104 0.189 5.26 × 104
4.00 × 104 0.252 7.02 × 104
5.00 × 104 0.315 8.77 × 104
6.00 × 104 0.378 1.05 × 105
7.00 × 104 0.441 1.23 × 105
8.00 × 104 0.504 1.40 × 105
9.00 × 104 0.567 1.58 × 105
1.00 × 105 0.630 1.75 × 105
1.69 × 105 1.07 2.97 × 105
Steel I Beam: W18 × 40 (Wide Flange 18 inch tall × 40 lbf/ft)
L = 15.0 ft
P (lbf/ft) w_max (in) stress_max (psi)
40.0 0.00128 158
50.0 0.00160 197
60.0 0.00191 237
70.0 0.00223 276
80.0 0.00255 316
90.0 0.00287 355
100 0.00319 395
200 0.00638 790
300 0.00957 1180
400 0.0128 1580
500 0.0160 1970
600 0.0191 2370
700 0.0223 2760
800 0.0255 3160
900 0.0287 3550
1000 0.0319 3950
2000 0.0638 7900
3000 0.0957 1.18 × 104
4000 0.128 1.58 × 104
5000 0.160 1.97 × 104
6000 0.191 2.37 × 104
7000 0.223 2.76 × 104
8000 0.255 3.16 × 104
9000 0.287 3.55 × 104
1.00 × 104 0.319 3.95 × 104
2.00 × 104 0.638 7.90 × 104
3.00 × 104 0.957 1.18 × 105
4.00 × 104 1.28 1.58 × 105
5.00 × 104 1.60 1.97 × 105
6.00 × 104 1.91 2.37 × 105
7.00 × 104 2.23 2.76 × 105
7.52 × 104 2.40 2.97 × 105
Steel I Beam: W18 × 40 (Wide Flange 18 inch tall × 40 lbf/ft)
L = 20.0 ft
P (lbf/ft) w_max (in) stress_max (psi)
40.0 0.00403 281
50.0 0.00504 351
60.0 0.00605 421
70.0 0.00706 491
80.0 0.00807 562
90.0 0.00908 632
100 0.0101 702
200 0.0202 1400
300 0.0303 2110
400 0.0403 2810
500 0.0504 3510
600 0.0605 4210
700 0.0706 4910
800 0.0807 5620
900 0.0908 6320
1000 0.101 7020
2000 0.202 1.40 × 104
3000 0.303 2.11 × 104
4000 0.403 2.81 × 104
5000 0.504 3.51 × 104
6000 0.605 4.21 × 104
7000 0.706 4.91 × 104
8000 0.807 5.62 × 104
9000 0.908 6.32 × 104
1.00 × 104 1.01 7.02 × 104
2.00 × 104 2.02 1.40 × 105
3.00 × 104 3.03 2.11 × 105
4.00 × 104 4.03 2.81 × 105
4.23 × 104 4.27 2.97 × 105
Steel I Beam: W18 × 40 (Wide Flange 18 inch tall × 40 lbf/ft)
L = 25.0 ft
P (lbf/ft) w_max (in) stress_max (psi)
40.0 0.00985 439
50.0 0.0123 548
60.0 0.0148 658
70.0 0.0172 768
80.0 0.0197 877
90.0 0.0222 987
100 0.0246 1100
200 0.0492 2190
300 0.0739 3290
400 0.0985 4390
500 0.123 5480
600 0.148 6580
700 0.172 7680
800 0.197 8770
900 0.222 9870
1000 0.246 1.10 × 104
2000 0.492 2.19 × 104
3000 0.739 3.29 × 104
4000 0.985 4.39 × 104
5000 1.23 5.48 × 104
6000 1.48 6.58 × 104
7000 1.72 7.68 × 104
8000 1.97 8.77 × 104
9000 2.22 9.87 × 104
1.00 × 104 2.46 1.10 × 105
2.00 × 104 4.92 2.19 × 105
2.71 × 104 6.67 2.97 × 105
Steel I Beam: W18 × 40 (Wide Flange 18 inch tall × 40 lbf/ft)
L = 30.0 ft
P (lbf/ft) w_max (in) stress_max (psi)
40.0 0.0204 632
50.0 0.0255 790
60.0 0.0306 948
70.0 0.0357 1110
80.0 0.0408 1260
90.0 0.0460 1420
100 0.0511 1580
200 0.102 3160
300 0.153 4740
400 0.204 6320
500 0.255 7900
600 0.306 9480
700 0.357 1.11 × 104
800 0.408 1.26 × 104
900 0.460 1.42 × 104
1000 0.511 1.58 × 104
2000 1.02 3.16 × 104
3000 1.53 4.74 × 104
4000 2.04 6.32 × 104
5000 2.55 7.90 × 104
6000 3.06 9.48 × 104
7000 3.57 1.11 × 105
8000 4.08 1.26 × 105
9000 4.60 1.42 × 105
1.00 × 104 5.11 1.58 × 105
1.88 × 104 9.60 2.97 × 105
Steel I Beam: W18 × 40 (Wide Flange 18 inch tall × 40 lbf/ft)
L = 40.0 ft
P (lbf/ft) w_max (in) stress_max (psi)
40.0 0.0646 1120
50.0 0.0807 1400
60.0 0.0968 1680
70.0 0.113 1970
80.0 0.129 2250
90.0 0.145 2530
100 0.161 2810
200 0.323 5620
300 0.484 8420
400 0.646 1.12 × 104
500 0.807 1.40 × 104
600 0.968 1.68 × 104
700 1.13 1.97 × 104
800 1.29 2.25 × 104
900 1.45 2.53 × 104
1000 1.61 2.81 × 104
2000 3.23 5.62 × 104
3000 4.84 8.42 × 104
4000 6.46 1.12 × 105
5000 8.07 1.40 × 105
6000 9.68 1.68 × 105
7000 11.3 1.97 × 105
8000 12.9 2.25 × 105
9000 14.5 2.53 × 105
1.00 × 104 16.1 2.81 × 105
1.06 × 104 17.1 2.97 × 105
Steel I Beam: W18 × 40 (Wide Flange 18 inch tall × 40 lbf/ft)
L = 50.0 ft
P (lbf/ft) w_max (in) stress_max (psi)
40.0 0.158 1750
50.0 0.197 2190
60.0 0.236 2630
70.0 0.276 3070
80.0 0.315 3510
90.0 0.355 3950
100 0.394 4390
200 0.788 8770
300 1.18 1.32 × 104
400 1.58 1.75 × 104
500 1.97 2.19 × 104
600 2.36 2.63 × 104
700 2.76 3.07 × 104
800 3.15 3.51 × 104
900 3.55 3.95 × 104
1000 3.94 4.39 × 104
2000 7.88 8.77 × 104
3000 11.8 1.32 × 105
4000 15.8 1.75 × 105
4540 17.9 1.99 × 105
Steel I Beam: W18 × 40 (Wide Flange 18 inch tall × 40 lbf/ft)
L = 60.0 ft
P (lbf/ft) w_max (in) stress_max (psi)
40.0 0.327 2530
50.0 0.408 3160
60.0 0.490 3790
70.0 0.572 4420
80.0 0.654 5050
90.0 0.735 5690
100 0.817 6320
200 1.63 1.26 × 104
300 2.45 1.90 × 104
400 3.27 2.53 × 104
500 4.08 3.16 × 104
600 4.90 3.79 × 104
700 5.72 4.42 × 104
800 6.54 5.05 × 104
900 7.35 5.69 × 104
1000 8.17 6.32 × 104
2000 16.3 1.26 × 105
2190 17.9 1.38 × 105
Steel I Beam: W18 × 40 (Wide Flange 18 inch tall × 40 lbf/ft)
L = 70.0 ft
P (lbf/ft) w_max (in) stress_max (psi)
40.0 0.605 3440
50.0 0.757 4300
60.0 0.908 5160
70.0 1.06 6020
80.0 1.21 6880
90.0 1.36 7740
100 1.51 8600
200 3.03 1.72 × 104
300 4.54 2.58 × 104
400 6.05 3.44 × 104
500 7.57 4.30 × 104
600 9.08 5.16 × 104
700 10.6 6.02 × 104
800 12.1 6.88 × 104
900 13.6 7.74 × 104
1000 15.1 8.60 × 104
1180 17.9 1.02 × 105
Steel I Beam: W18 × 40 (Wide Flange 18 inch tall × 40 lbf/ft)
L = 80.0 ft
P (lbf/ft) w_max (in) stress_max (psi)
40.0 1.03 4490
50.0 1.29 5620
60.0 1.55 6740
70.0 1.81 7860
80.0 2.07 8990
90.0 2.32 1.01 × 104
100 2.58 1.12 × 104
200 5.16 2.25 × 104
300 7.75 3.37 × 104
400 10.3 4.49 × 104
500 12.9 5.62 × 104
600 15.5 6.74 × 104
693 17.9 7.79 × 104
Steel I Beam: W18 × 40 (Wide Flange 18 inch tall × 40 lbf/ft)
L = 90.0 ft
P (lbf/ft) w_max (in) stress_max (psi)
40.0 1.65 5690
50.0 2.07 7110
60.0 2.48 8530
70.0 2.90 9950
80.0 3.31 1.14 × 104
90.0 3.72 1.28 × 104
100 4.14 1.42 × 104
200 8.27 2.84 × 104
300 12.4 4.26 × 104
400 16.5 5.69 × 104
433 17.9 6.15 × 104
Steel I Beam: W18 × 40 (Wide Flange 18 inch tall × 40 lbf/ft)
L = 100 ft
P (lbf/ft) w_max (in) stress_max (psi)
40.0 2.52 7020
50.0 3.15 8770
60.0 3.78 1.05 × 104
70.0 4.41 1.23 × 104
80.0 5.04 1.40 × 104
90.0 5.67 1.58 × 104
100 6.30 1.75 × 104
200 12.6 3.51 × 104
284 17.9 4.98 × 104
Steel I Beam: W18 × 40 (Wide Flange 18 inch tall × 40 lbf/ft)
L = 125 ft
P (lbf/ft) w_max (in) stress_max (psi)
40.0 6.16 1.10 × 104
50.0 7.70 1.37 × 104
60.0 9.23 1.65 × 104
70.0 10.8 1.92 × 104
80.0 12.3 2.19 × 104
90.0 13.9 2.47 × 104
100 15.4 2.74 × 104
116 17.9 3.19 × 104
Steel I Beam: W18 × 40 (Wide Flange 18 inch tall × 40 lbf/ft)
L = 150 ft
P (lbf/ft) w_max (in) stress_max (psi)
40.0 12.8 1.58 × 104
50.0 16.0 1.97 × 104
56.1 17.9 2.21 × 104
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