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Glossary » Beams » Simply Supported » Uniformly Distributed Load » Two Equal Spans » Wide Flange Steel I Beam » W21 × 73
Wide Flange Steel I Beam | Single Span | Two Equal Spans | Three Equal Spans | Four Equal Spans

For a simply supported beam in two equal spans, we compute the displacement at the middle of each span w_mid and the maximum normal stress stress_max occuring at the center support of the beam.
The tabulated data listed in this page are calculated based on the area moment of inertia (Ixx = 1600 in4) for the W21 × 73 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: W21 × 73 (Wide Flange 21 inch tall × 73 lbf/ft)
L = 3.00 ft
P (lbf/ft) w_max (in) stress_max (psi)
73.0 1.09 × 10-6 6.54
80.0 1.20 × 10-6 7.17
90.0 1.35 × 10-6 8.06
100 1.50 × 10-6 8.96
200 2.99 × 10-6 17.9
300 4.49 × 10-6 26.9
400 5.98 × 10-6 35.8
500 7.48 × 10-6 44.8
600 8.98 × 10-6 53.8
700 1.05 × 10-5 62.7
800 1.20 × 10-5 71.7
900 1.35 × 10-5 80.6
1000 1.50 × 10-5 89.6
2000 2.99 × 10-5 179
3000 4.49 × 10-5 269
4000 5.98 × 10-5 358
5000 7.48 × 10-5 448
6000 8.98 × 10-5 538
7000 1.05 × 10-4 627
8000 1.20 × 10-4 717
9000 1.35 × 10-4 806
1.00 × 104 1.50 × 10-4 896
2.00 × 104 2.99 × 10-4 1790
3.00 × 104 4.49 × 10-4 2690
4.00 × 104 5.98 × 10-4 3580
5.00 × 104 7.48 × 10-4 4480
6.00 × 104 8.98 × 10-4 5380
7.00 × 104 0.00105 6270
8.00 × 104 0.00120 7170
9.00 × 104 0.00135 8060
1.00 × 105 0.00150 8960
2.00 × 105 0.00299 1.79 × 104
3.00 × 105 0.00449 2.69 × 104
4.00 × 105 0.00598 3.58 × 104
5.00 × 105 0.00748 4.48 × 104
6.00 × 105 0.00898 5.38 × 104
7.00 × 105 0.0105 6.27 × 104
8.00 × 105 0.0120 7.17 × 104
9.00 × 105 0.0135 8.06 × 104
1.00 × 106 0.0150 8.96 × 104
2.00 × 106 0.0299 1.79 × 105
3.00 × 106 0.0449 2.69 × 105
3.31 × 106 0.0496 2.97 × 105
Steel I Beam: W21 × 73 (Wide Flange 21 inch tall × 73 lbf/ft)
L = 5.00 ft
P (lbf/ft) w_max (in) stress_max (psi)
73.0 8.43 × 10-6 18.2
80.0 9.23 × 10-6 19.9
90.0 1.04 × 10-5 22.4
100 1.15 × 10-5 24.9
200 2.31 × 10-5 49.8
300 3.46 × 10-5 74.7
400 4.62 × 10-5 99.6
500 5.77 × 10-5 124
600 6.93 × 10-5 149
700 8.08 × 10-5 174
800 9.23 × 10-5 199
900 1.04 × 10-4 224
1000 1.15 × 10-4 249
2000 2.31 × 10-4 498
3000 3.46 × 10-4 747
4000 4.62 × 10-4 996
5000 5.77 × 10-4 1240
6000 6.93 × 10-4 1490
7000 8.08 × 10-4 1740
8000 9.23 × 10-4 1990
9000 0.00104 2240
1.00 × 104 0.00115 2490
2.00 × 104 0.00231 4980
3.00 × 104 0.00346 7470
4.00 × 104 0.00462 9960
5.00 × 104 0.00577 1.24 × 104
6.00 × 104 0.00693 1.49 × 104
7.00 × 104 0.00808 1.74 × 104
8.00 × 104 0.00923 1.99 × 104
9.00 × 104 0.0104 2.24 × 104
1.00 × 105 0.0115 2.49 × 104
2.00 × 105 0.0231 4.98 × 104
3.00 × 105 0.0346 7.47 × 104
4.00 × 105 0.0462 9.96 × 104
5.00 × 105 0.0577 1.24 × 105
6.00 × 105 0.0693 1.49 × 105
7.00 × 105 0.0808 1.74 × 105
8.00 × 105 0.0923 1.99 × 105
9.00 × 105 0.104 2.24 × 105
1.00 × 106 0.115 2.49 × 105
1.19 × 106 0.138 2.97 × 105
Steel I Beam: W21 × 73 (Wide Flange 21 inch tall × 73 lbf/ft)
L = 10.0 ft
P (lbf/ft) w_max (in) stress_max (psi)
73.0 1.35 × 10-4 72.7
80.0 1.48 × 10-4 79.6
90.0 1.66 × 10-4 89.6
100 1.85 × 10-4 99.6
200 3.69 × 10-4 199
300 5.54 × 10-4 299
400 7.39 × 10-4 398
500 9.23 × 10-4 498
600 0.00111 597
700 0.00129 697
800 0.00148 797
900 0.00166 896
1000 0.00185 996
2000 0.00369 1990
3000 0.00554 2990
4000 0.00739 3980
5000 0.00923 4980
6000 0.0111 5970
7000 0.0129 6970
8000 0.0148 7960
9000 0.0166 8960
1.00 × 104 0.0185 9960
2.00 × 104 0.0369 1.99 × 104
3.00 × 104 0.0554 2.99 × 104
4.00 × 104 0.0739 3.98 × 104
5.00 × 104 0.0923 4.98 × 104
6.00 × 104 0.111 5.97 × 104
7.00 × 104 0.129 6.97 × 104
8.00 × 104 0.148 7.96 × 104
9.00 × 104 0.166 8.96 × 104
1.00 × 105 0.185 9.96 × 104
2.00 × 105 0.369 1.99 × 105
2.98 × 105 0.551 2.97 × 105
Steel I Beam: W21 × 73 (Wide Flange 21 inch tall × 73 lbf/ft)
L = 15.0 ft
P (lbf/ft) w_max (in) stress_max (psi)
73.0 6.83 × 10-4 164
80.0 7.48 × 10-4 179
90.0 8.41 × 10-4 202
100 9.35 × 10-4 224
200 0.00187 448
300 0.00280 672
400 0.00374 896
500 0.00467 1120
600 0.00561 1340
700 0.00654 1570
800 0.00748 1790
900 0.00841 2020
1000 0.00935 2240
2000 0.0187 4480
3000 0.0280 6720
4000 0.0374 8960
5000 0.0467 1.12 × 104
6000 0.0561 1.34 × 104
7000 0.0654 1.57 × 104
8000 0.0748 1.79 × 104
9000 0.0841 2.02 × 104
1.00 × 104 0.0935 2.24 × 104
2.00 × 104 0.187 4.48 × 104
3.00 × 104 0.280 6.72 × 104
4.00 × 104 0.374 8.96 × 104
5.00 × 104 0.467 1.12 × 105
6.00 × 104 0.561 1.34 × 105
7.00 × 104 0.654 1.57 × 105
8.00 × 104 0.748 1.79 × 105
9.00 × 104 0.841 2.02 × 105
1.00 × 105 0.935 2.24 × 105
1.33 × 105 1.24 2.97 × 105
Steel I Beam: W21 × 73 (Wide Flange 21 inch tall × 73 lbf/ft)
L = 20.0 ft
P (lbf/ft) w_max (in) stress_max (psi)
73.0 0.00216 291
80.0 0.00236 319
90.0 0.00266 358
100 0.00295 398
200 0.00591 797
300 0.00886 1190
400 0.0118 1590
500 0.0148 1990
600 0.0177 2390
700 0.0207 2790
800 0.0236 3190
900 0.0266 3580
1000 0.0295 3980
2000 0.0591 7960
3000 0.0886 1.19 × 104
4000 0.118 1.59 × 104
5000 0.148 1.99 × 104
6000 0.177 2.39 × 104
7000 0.207 2.79 × 104
8000 0.236 3.19 × 104
9000 0.266 3.58 × 104
1.00 × 104 0.295 3.98 × 104
2.00 × 104 0.591 7.96 × 104
3.00 × 104 0.886 1.19 × 105
4.00 × 104 1.18 1.59 × 105
5.00 × 104 1.48 1.99 × 105
6.00 × 104 1.77 2.39 × 105
7.00 × 104 2.07 2.79 × 105
7.46 × 104 2.20 2.97 × 105
Steel I Beam: W21 × 73 (Wide Flange 21 inch tall × 73 lbf/ft)
L = 25.0 ft
P (lbf/ft) w_max (in) stress_max (psi)
73.0 0.00527 454
80.0 0.00577 498
90.0 0.00649 560
100 0.00721 622
200 0.0144 1240
300 0.0216 1870
400 0.0289 2490
500 0.0361 3110
600 0.0433 3730
700 0.0505 4360
800 0.0577 4980
900 0.0649 5600
1000 0.0721 6220
2000 0.144 1.24 × 104
3000 0.216 1.87 × 104
4000 0.289 2.49 × 104
5000 0.361 3.11 × 104
6000 0.433 3.73 × 104
7000 0.505 4.36 × 104
8000 0.577 4.98 × 104
9000 0.649 5.60 × 104
1.00 × 104 0.721 6.22 × 104
2.00 × 104 1.44 1.24 × 105
3.00 × 104 2.16 1.87 × 105
4.00 × 104 2.89 2.49 × 105
4.77 × 104 3.44 2.97 × 105
Steel I Beam: W21 × 73 (Wide Flange 21 inch tall × 73 lbf/ft)
L = 30.0 ft
P (lbf/ft) w_max (in) stress_max (psi)
73.0 0.0109 654
80.0 0.0120 717
90.0 0.0135 806
100 0.0150 896
200 0.0299 1790
300 0.0449 2690
400 0.0598 3580
500 0.0748 4480
600 0.0898 5380
700 0.105 6270
800 0.120 7170
900 0.135 8060
1000 0.150 8960
2000 0.299 1.79 × 104
3000 0.449 2.69 × 104
4000 0.598 3.58 × 104
5000 0.748 4.48 × 104
6000 0.898 5.38 × 104
7000 1.05 6.27 × 104
8000 1.20 7.17 × 104
9000 1.35 8.06 × 104
1.00 × 104 1.50 8.96 × 104
2.00 × 104 2.99 1.79 × 105
3.00 × 104 4.49 2.69 × 105
3.31 × 104 4.96 2.97 × 105
Steel I Beam: W21 × 73 (Wide Flange 21 inch tall × 73 lbf/ft)
L = 40.0 ft
P (lbf/ft) w_max (in) stress_max (psi)
73.0 0.0345 1160
80.0 0.0378 1270
90.0 0.0426 1430
100 0.0473 1590
200 0.0946 3190
300 0.142 4780
400 0.189 6370
500 0.236 7960
600 0.284 9560
700 0.331 1.12 × 104
800 0.378 1.27 × 104
900 0.426 1.43 × 104
1000 0.473 1.59 × 104
2000 0.946 3.19 × 104
3000 1.42 4.78 × 104
4000 1.89 6.37 × 104
5000 2.36 7.96 × 104
6000 2.84 9.56 × 104
7000 3.31 1.12 × 105
8000 3.78 1.27 × 105
9000 4.26 1.43 × 105
1.00 × 104 4.73 1.59 × 105
1.86 × 104 8.82 2.97 × 105
Steel I Beam: W21 × 73 (Wide Flange 21 inch tall × 73 lbf/ft)
L = 50.0 ft
P (lbf/ft) w_max (in) stress_max (psi)
73.0 0.0843 1820
80.0 0.0923 1990
90.0 0.104 2240
100 0.115 2490
200 0.231 4980
300 0.346 7470
400 0.462 9960
500 0.577 1.24 × 104
600 0.693 1.49 × 104
700 0.808 1.74 × 104
800 0.923 1.99 × 104
900 1.04 2.24 × 104
1000 1.15 2.49 × 104
2000 2.31 4.98 × 104
3000 3.46 7.47 × 104
4000 4.62 9.96 × 104
5000 5.77 1.24 × 105
6000 6.93 1.49 × 105
7000 8.08 1.74 × 105
8000 9.23 1.99 × 105
9000 10.4 2.24 × 105
1.00 × 104 11.5 2.49 × 105
1.19 × 104 13.8 2.97 × 105
Steel I Beam: W21 × 73 (Wide Flange 21 inch tall × 73 lbf/ft)
L = 60.0 ft
P (lbf/ft) w_max (in) stress_max (psi)
73.0 0.175 2620
80.0 0.191 2870
90.0 0.215 3230
100 0.239 3580
200 0.479 7170
300 0.718 1.08 × 104
400 0.957 1.43 × 104
500 1.20 1.79 × 104
600 1.44 2.15 × 104
700 1.68 2.51 × 104
800 1.91 2.87 × 104
900 2.15 3.23 × 104
1000 2.39 3.58 × 104
2000 4.79 7.17 × 104
3000 7.18 1.08 × 105
4000 9.57 1.43 × 105
5000 12.0 1.79 × 105
6000 14.4 2.15 × 105
7000 16.8 2.51 × 105
8000 19.1 2.87 × 105
8290 19.8 2.97 × 105
Steel I Beam: W21 × 73 (Wide Flange 21 inch tall × 73 lbf/ft)
L = 70.0 ft
P (lbf/ft) w_max (in) stress_max (psi)
73.0 0.324 3560
80.0 0.355 3900
90.0 0.399 4390
100 0.443 4880
200 0.887 9760
300 1.33 1.46 × 104
400 1.77 1.95 × 104
500 2.22 2.44 × 104
600 2.66 2.93 × 104
700 3.10 3.41 × 104
800 3.55 3.90 × 104
900 3.99 4.39 × 104
1000 4.43 4.88 × 104
2000 8.87 9.76 × 104
3000 13.3 1.46 × 105
4000 17.7 1.95 × 105
4790 21.2 2.34 × 105
Steel I Beam: W21 × 73 (Wide Flange 21 inch tall × 73 lbf/ft)
L = 80.0 ft
P (lbf/ft) w_max (in) stress_max (psi)
73.0 0.552 4650
80.0 0.605 5100
90.0 0.681 5730
100 0.756 6370
200 1.51 1.27 × 104
300 2.27 1.91 × 104
400 3.03 2.55 × 104
500 3.78 3.19 × 104
600 4.54 3.82 × 104
700 5.30 4.46 × 104
800 6.05 5.10 × 104
900 6.81 5.73 × 104
1000 7.56 6.37 × 104
2000 15.1 1.27 × 105
2810 21.2 1.79 × 105
Steel I Beam: W21 × 73 (Wide Flange 21 inch tall × 73 lbf/ft)
L = 90.0 ft
P (lbf/ft) w_max (in) stress_max (psi)
73.0 0.885 5890
80.0 0.969 6450
90.0 1.09 7260
100 1.21 8060
200 2.42 1.61 × 104
300 3.64 2.42 × 104
400 4.85 3.23 × 104
500 6.06 4.03 × 104
600 7.27 4.84 × 104
700 8.48 5.65 × 104
800 9.69 6.45 × 104
900 10.9 7.26 × 104
1000 12.1 8.06 × 104
1750 21.2 1.41 × 105
Steel I Beam: W21 × 73 (Wide Flange 21 inch tall × 73 lbf/ft)
L = 100 ft
P (lbf/ft) w_max (in) stress_max (psi)
73.0 1.35 7270
80.0 1.48 7960
90.0 1.66 8960
100 1.85 9960
200 3.69 1.99 × 104
300 5.54 2.99 × 104
400 7.39 3.98 × 104
500 9.23 4.98 × 104
600 11.1 5.97 × 104
700 12.9 6.97 × 104
800 14.8 7.96 × 104
900 16.6 8.96 × 104
1000 18.5 9.96 × 104
1150 21.2 1.15 × 105
Steel I Beam: W21 × 73 (Wide Flange 21 inch tall × 73 lbf/ft)
L = 125 ft
P (lbf/ft) w_max (in) stress_max (psi)
73.0 3.29 1.14 × 104
80.0 3.61 1.24 × 104
90.0 4.06 1.40 × 104
100 4.51 1.56 × 104
200 9.02 3.11 × 104
300 13.5 4.67 × 104
400 18.0 6.22 × 104
471 21.2 7.33 × 104
Steel I Beam: W21 × 73 (Wide Flange 21 inch tall × 73 lbf/ft)
L = 150 ft
P (lbf/ft) w_max (in) stress_max (psi)
73.0 6.83 1.64 × 104
80.0 7.48 1.79 × 104
90.0 8.41 2.02 × 104
100 9.35 2.24 × 104
200 18.7 4.48 × 104
227 21.2 5.09 × 104
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STEM Career Outlook

Wages, employment opportunities, and growth projections for STEM jobs.

Essentials of Manufacturing

Information, coverage of important developments and expert commentary in manufacturing.

Mechanical Engineers Outlook

Guide for those interested in becoming a mechanical engineer. Includes qualifications, pay, and job duties.

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