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Glossary » Beams » Simply Supported » Uniformly Distributed Load » Three Equal Spans » Wide Flange Steel I Beam » W21 × 122
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 = 2960 in4) for the W21 × 122 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 × 122 (Wide Flange 21 inch tall × 122 lbf/ft)
L = 3.00 ft
P (lbf/ft) w_max (in) stress_max (psi)
122 1.29 × 10-6 4.83
200 2.11 × 10-6 7.91
300 3.17 × 10-6 11.9
400 4.22 × 10-6 15.8
500 5.28 × 10-6 19.8
600 6.33 × 10-6 23.7
700 7.39 × 10-6 27.7
800 8.45 × 10-6 31.6
900 9.50 × 10-6 35.6
1000 1.06 × 10-5 39.6
2000 2.11 × 10-5 79.1
3000 3.17 × 10-5 119
4000 4.22 × 10-5 158
5000 5.28 × 10-5 198
6000 6.33 × 10-5 237
7000 7.39 × 10-5 277
8000 8.45 × 10-5 316
9000 9.50 × 10-5 356
1.00 × 104 1.06 × 10-4 396
2.00 × 104 2.11 × 10-4 791
3.00 × 104 3.17 × 10-4 1190
4.00 × 104 4.22 × 10-4 1580
5.00 × 104 5.28 × 10-4 1980
6.00 × 104 6.33 × 10-4 2370
7.00 × 104 7.39 × 10-4 2770
8.00 × 104 8.45 × 10-4 3160
9.00 × 104 9.50 × 10-4 3560
1.00 × 105 0.00106 3960
2.00 × 105 0.00211 7910
3.00 × 105 0.00317 1.19 × 104
4.00 × 105 0.00422 1.58 × 104
5.00 × 105 0.00528 1.98 × 104
6.00 × 105 0.00633 2.37 × 104
7.00 × 105 0.00739 2.77 × 104
8.00 × 105 0.00845 3.16 × 104
9.00 × 105 0.00950 3.56 × 104
1.00 × 106 0.0106 3.96 × 104
2.00 × 106 0.0211 7.91 × 104
3.00 × 106 0.0317 1.19 × 105
4.00 × 106 0.0422 1.58 × 105
5.00 × 106 0.0528 1.98 × 105
6.00 × 106 0.0633 2.37 × 105
7.00 × 106 0.0739 2.77 × 105
7.51 × 106 0.0793 2.97 × 105
Steel I Beam: W21 × 122 (Wide Flange 21 inch tall × 122 lbf/ft)
L = 5.00 ft
P (lbf/ft) w_max (in) stress_max (psi)
122 9.94 × 10-6 13.4
200 1.63 × 10-5 22.0
300 2.44 × 10-5 33.0
400 3.26 × 10-5 43.9
500 4.07 × 10-5 54.9
600 4.89 × 10-5 65.9
700 5.70 × 10-5 76.9
800 6.52 × 10-5 87.9
900 7.33 × 10-5 98.9
1000 8.15 × 10-5 110
2000 1.63 × 10-4 220
3000 2.44 × 10-4 330
4000 3.26 × 10-4 439
5000 4.07 × 10-4 549
6000 4.89 × 10-4 659
7000 5.70 × 10-4 769
8000 6.52 × 10-4 879
9000 7.33 × 10-4 989
1.00 × 104 8.15 × 10-4 1100
2.00 × 104 0.00163 2200
3.00 × 104 0.00244 3300
4.00 × 104 0.00326 4390
5.00 × 104 0.00407 5490
6.00 × 104 0.00489 6590
7.00 × 104 0.00570 7690
8.00 × 104 0.00652 8790
9.00 × 104 0.00733 9890
1.00 × 105 0.00815 1.10 × 104
2.00 × 105 0.0163 2.20 × 104
3.00 × 105 0.0244 3.30 × 104
4.00 × 105 0.0326 4.39 × 104
5.00 × 105 0.0407 5.49 × 104
6.00 × 105 0.0489 6.59 × 104
7.00 × 105 0.0570 7.69 × 104
8.00 × 105 0.0652 8.79 × 104
9.00 × 105 0.0733 9.89 × 104
1.00 × 106 0.0815 1.10 × 105
2.00 × 106 0.163 2.20 × 105
2.70 × 106 0.220 2.97 × 105
Steel I Beam: W21 × 122 (Wide Flange 21 inch tall × 122 lbf/ft)
L = 10.0 ft
P (lbf/ft) w_max (in) stress_max (psi)
122 1.59 × 10-4 53.6
200 2.61 × 10-4 87.9
300 3.91 × 10-4 132
400 5.21 × 10-4 176
500 6.52 × 10-4 220
600 7.82 × 10-4 264
700 9.12 × 10-4 308
800 0.00104 352
900 0.00117 396
1000 0.00130 439
2000 0.00261 879
3000 0.00391 1320
4000 0.00521 1760
5000 0.00652 2200
6000 0.00782 2640
7000 0.00912 3080
8000 0.0104 3520
9000 0.0117 3960
1.00 × 104 0.0130 4390
2.00 × 104 0.0261 8790
3.00 × 104 0.0391 1.32 × 104
4.00 × 104 0.0521 1.76 × 104
5.00 × 104 0.0652 2.20 × 104
6.00 × 104 0.0782 2.64 × 104
7.00 × 104 0.0912 3.08 × 104
8.00 × 104 0.104 3.52 × 104
9.00 × 104 0.117 3.96 × 104
1.00 × 105 0.130 4.39 × 104
2.00 × 105 0.261 8.79 × 104
3.00 × 105 0.391 1.32 × 105
4.00 × 105 0.521 1.76 × 105
5.00 × 105 0.652 2.20 × 105
6.00 × 105 0.782 2.64 × 105
6.76 × 105 0.881 2.97 × 105
Steel I Beam: W21 × 122 (Wide Flange 21 inch tall × 122 lbf/ft)
L = 15.0 ft
P (lbf/ft) w_max (in) stress_max (psi)
122 8.05 × 10-4 121
200 0.00132 198
300 0.00198 297
400 0.00264 396
500 0.00330 494
600 0.00396 593
700 0.00462 692
800 0.00528 791
900 0.00594 890
1000 0.00660 989
2000 0.0132 1980
3000 0.0198 2970
4000 0.0264 3960
5000 0.0330 4940
6000 0.0396 5930
7000 0.0462 6920
8000 0.0528 7910
9000 0.0594 8900
1.00 × 104 0.0660 9890
2.00 × 104 0.132 1.98 × 104
3.00 × 104 0.198 2.97 × 104
4.00 × 104 0.264 3.96 × 104
5.00 × 104 0.330 4.94 × 104
6.00 × 104 0.396 5.93 × 104
7.00 × 104 0.462 6.92 × 104
8.00 × 104 0.528 7.91 × 104
9.00 × 104 0.594 8.90 × 104
1.00 × 105 0.660 9.89 × 104
2.00 × 105 1.32 1.98 × 105
3.00 × 105 1.98 2.97 × 105
3.00 × 105 1.98 2.97 × 105
Steel I Beam: W21 × 122 (Wide Flange 21 inch tall × 122 lbf/ft)
L = 20.0 ft
P (lbf/ft) w_max (in) stress_max (psi)
122 0.00254 214
200 0.00417 352
300 0.00626 527
400 0.00834 703
500 0.0104 879
600 0.0125 1050
700 0.0146 1230
800 0.0167 1410
900 0.0188 1580
1000 0.0209 1760
2000 0.0417 3520
3000 0.0626 5270
4000 0.0834 7030
5000 0.104 8790
6000 0.125 1.05 × 104
7000 0.146 1.23 × 104
8000 0.167 1.41 × 104
9000 0.188 1.58 × 104
1.00 × 104 0.209 1.76 × 104
2.00 × 104 0.417 3.52 × 104
3.00 × 104 0.626 5.27 × 104
4.00 × 104 0.834 7.03 × 104
5.00 × 104 1.04 8.79 × 104
6.00 × 104 1.25 1.05 × 105
7.00 × 104 1.46 1.23 × 105
8.00 × 104 1.67 1.41 × 105
9.00 × 104 1.88 1.58 × 105
1.00 × 105 2.09 1.76 × 105
1.69 × 105 3.52 2.97 × 105
Steel I Beam: W21 × 122 (Wide Flange 21 inch tall × 122 lbf/ft)
L = 25.0 ft
P (lbf/ft) w_max (in) stress_max (psi)
122 0.00621 335
200 0.0102 549
300 0.0153 824
400 0.0204 1100
500 0.0255 1370
600 0.0305 1650
700 0.0356 1920
800 0.0407 2200
900 0.0458 2470
1000 0.0509 2750
2000 0.102 5490
3000 0.153 8240
4000 0.204 1.10 × 104
5000 0.255 1.37 × 104
6000 0.305 1.65 × 104
7000 0.356 1.92 × 104
8000 0.407 2.20 × 104
9000 0.458 2.47 × 104
1.00 × 104 0.509 2.75 × 104
2.00 × 104 1.02 5.49 × 104
3.00 × 104 1.53 8.24 × 104
4.00 × 104 2.04 1.10 × 105
5.00 × 104 2.55 1.37 × 105
6.00 × 104 3.05 1.65 × 105
7.00 × 104 3.56 1.92 × 105
8.00 × 104 4.07 2.20 × 105
9.00 × 104 4.58 2.47 × 105
1.00 × 105 5.09 2.75 × 105
1.08 × 105 5.51 2.97 × 105
Steel I Beam: W21 × 122 (Wide Flange 21 inch tall × 122 lbf/ft)
L = 30.0 ft
P (lbf/ft) w_max (in) stress_max (psi)
122 0.0129 483
200 0.0211 791
300 0.0317 1190
400 0.0422 1580
500 0.0528 1980
600 0.0633 2370
700 0.0739 2770
800 0.0845 3160
900 0.0950 3560
1000 0.106 3960
2000 0.211 7910
3000 0.317 1.19 × 104
4000 0.422 1.58 × 104
5000 0.528 1.98 × 104
6000 0.633 2.37 × 104
7000 0.739 2.77 × 104
8000 0.845 3.16 × 104
9000 0.950 3.56 × 104
1.00 × 104 1.06 3.96 × 104
2.00 × 104 2.11 7.91 × 104
3.00 × 104 3.17 1.19 × 105
4.00 × 104 4.22 1.58 × 105
5.00 × 104 5.28 1.98 × 105
6.00 × 104 6.33 2.37 × 105
7.00 × 104 7.39 2.77 × 105
7.51 × 104 7.93 2.97 × 105
Steel I Beam: W21 × 122 (Wide Flange 21 inch tall × 122 lbf/ft)
L = 40.0 ft
P (lbf/ft) w_max (in) stress_max (psi)
122 0.0407 858
200 0.0667 1410
300 0.100 2110
400 0.133 2810
500 0.167 3520
600 0.200 4220
700 0.234 4920
800 0.267 5630
900 0.300 6330
1000 0.334 7030
2000 0.667 1.41 × 104
3000 1.00 2.11 × 104
4000 1.33 2.81 × 104
5000 1.67 3.52 × 104
6000 2.00 4.22 × 104
7000 2.34 4.92 × 104
8000 2.67 5.63 × 104
9000 3.00 6.33 × 104
1.00 × 104 3.34 7.03 × 104
2.00 × 104 6.67 1.41 × 105
3.00 × 104 10.0 2.11 × 105
4.00 × 104 13.3 2.81 × 105
4.22 × 104 14.1 2.97 × 105
Steel I Beam: W21 × 122 (Wide Flange 21 inch tall × 122 lbf/ft)
L = 50.0 ft
P (lbf/ft) w_max (in) stress_max (psi)
122 0.0994 1340
200 0.163 2200
300 0.244 3300
400 0.326 4390
500 0.407 5490
600 0.489 6590
700 0.570 7690
800 0.652 8790
900 0.733 9890
1000 0.815 1.10 × 104
2000 1.63 2.20 × 104
3000 2.44 3.30 × 104
4000 3.26 4.39 × 104
5000 4.07 5.49 × 104
6000 4.89 6.59 × 104
7000 5.70 7.69 × 104
8000 6.52 8.79 × 104
9000 7.33 9.89 × 104
1.00 × 104 8.15 1.10 × 105
2.00 × 104 16.3 2.20 × 105
2.70 × 104 22.0 2.97 × 105
Steel I Beam: W21 × 122 (Wide Flange 21 inch tall × 122 lbf/ft)
L = 60.0 ft
P (lbf/ft) w_max (in) stress_max (psi)
122 0.206 1930
200 0.338 3160
300 0.507 4750
400 0.676 6330
500 0.845 7910
600 1.01 9490
700 1.18 1.11 × 104
800 1.35 1.27 × 104
900 1.52 1.42 × 104
1000 1.69 1.58 × 104
2000 3.38 3.16 × 104
3000 5.07 4.75 × 104
4000 6.76 6.33 × 104
5000 8.45 7.91 × 104
6000 10.1 9.49 × 104
7000 11.8 1.11 × 105
8000 13.5 1.27 × 105
9000 15.2 1.42 × 105
1.00 × 104 16.9 1.58 × 105
1.88 × 104 31.7 2.97 × 105
Steel I Beam: W21 × 122 (Wide Flange 21 inch tall × 122 lbf/ft)
L = 70.0 ft
P (lbf/ft) w_max (in) stress_max (psi)
122 0.382 2630
200 0.626 4310
300 0.939 6460
400 1.25 8610
500 1.56 1.08 × 104
600 1.88 1.29 × 104
700 2.19 1.51 × 104
800 2.50 1.72 × 104
900 2.82 1.94 × 104
1000 3.13 2.15 × 104
2000 6.26 4.31 × 104
3000 9.39 6.46 × 104
4000 12.5 8.61 × 104
5000 15.6 1.08 × 105
6000 18.8 1.29 × 105
6930 21.7 1.49 × 105
Steel I Beam: W21 × 122 (Wide Flange 21 inch tall × 122 lbf/ft)
L = 80.0 ft
P (lbf/ft) w_max (in) stress_max (psi)
122 0.651 3430
200 1.07 5630
300 1.60 8440
400 2.14 1.13 × 104
500 2.67 1.41 × 104
600 3.20 1.69 × 104
700 3.74 1.97 × 104
800 4.27 2.25 × 104
900 4.80 2.53 × 104
1000 5.34 2.81 × 104
2000 10.7 5.63 × 104
3000 16.0 8.44 × 104
4000 21.4 1.13 × 105
4060 21.7 1.14 × 105
Steel I Beam: W21 × 122 (Wide Flange 21 inch tall × 122 lbf/ft)
L = 90.0 ft
P (lbf/ft) w_max (in) stress_max (psi)
122 1.04 4340
200 1.71 7120
300 2.57 1.07 × 104
400 3.42 1.42 × 104
500 4.28 1.78 × 104
600 5.13 2.14 × 104
700 5.99 2.49 × 104
800 6.84 2.85 × 104
900 7.70 3.20 × 104
1000 8.55 3.56 × 104
2000 17.1 7.12 × 104
2540 21.7 9.02 × 104
Steel I Beam: W21 × 122 (Wide Flange 21 inch tall × 122 lbf/ft)
L = 100 ft
P (lbf/ft) w_max (in) stress_max (psi)
122 1.59 5360
200 2.61 8790
300 3.91 1.32 × 104
400 5.21 1.76 × 104
500 6.52 2.20 × 104
600 7.82 2.64 × 104
700 9.12 3.08 × 104
800 10.4 3.52 × 104
900 11.7 3.96 × 104
1000 13.0 4.39 × 104
1660 21.7 7.31 × 104
Steel I Beam: W21 × 122 (Wide Flange 21 inch tall × 122 lbf/ft)
L = 125 ft
P (lbf/ft) w_max (in) stress_max (psi)
122 3.88 8380
200 6.36 1.37 × 104
300 9.55 2.06 × 104
400 12.7 2.75 × 104
500 15.9 3.43 × 104
600 19.1 4.12 × 104
681 21.7 4.68 × 104
Steel I Beam: W21 × 122 (Wide Flange 21 inch tall × 122 lbf/ft)
L = 150 ft
P (lbf/ft) w_max (in) stress_max (psi)
122 8.05 1.21 × 104
200 13.2 1.98 × 104
300 19.8 2.97 × 104
329 21.7 3.25 × 104
Additional Information
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Mechanical Engineers Outlook

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

STEM Career Outlook

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

Negotiate Your Salary

Learn the best principles to negotiate the salary you deserve!

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