Steel Design calculators
Steel connection and member checks: fillet weld throat and resistance, base plate area and thickness, column buckling and slenderness, beam span from the deflection limit, and section modulus. To EN 1993-1-8 and AISC Design Guide 1.
What this group solves
These are not the weight calculators. That group answers how heavy a section is and how much consumable a weld needs; this group answers whether the connection holds. In steel structures almost every failure is in a connection or a stability check rather than in the member — members are selected from tables, connections are made on site.
The four tools form one chain. The beam span tool back-calculates the inertia the deflection limit demands, the section properties tool checks whether the chosen profile has it, the column buckling tool asks whether the column fails first, and the fillet weld tool carries the force into the connection. The order matters: size the section before checking the weld, or you end up proving the weld is fine while the plate it sits on is not.
Three numbers are commonly wrong, and all three err on the unsafe side. A leg size is not a throat thickness — a 6 mm leg has a 4.2 mm throat and 43% less capacity. An effective length factor of 0.5 is theoretical; real fixity is hard to achieve. And a steel beam is usually governed by deflection rather than strength, so a section chosen on strength alone will bounce underfoot.
The biggest difference from concrete design is what governs. Concrete members are mostly strength-governed — get the reinforcement in and the section works. Steel members are mostly governed by deformation and stability, with strength often far from critical. So never stop at the strength check on steel: follow through to deflection for beams, slenderness for columns and detailing for connections. Skip that and the drawing calculates but the floor bounces.
The second thing easily missed is that the connection is weaker than the member. Steel failures happen almost entirely at connections: a fillet weld reaches half the parent metal strength, bolt bearing usually governs over shear, and the base plate hands load into concrete at a fifteenth of the steel strength. Design order therefore runs backwards — fix the connection type first and choose the member to suit, otherwise you end up with a section that cannot be connected and all the saving is spent on the joint.
Which one for your case
| Span and load known, need the beam depth | Steel Beam Span Calculator |
| Have a section size, need inertia and modulus | Section Properties Calculator |
| Will the column buckle first, and at what slenderness | Column Buckling Calculator |
| How much a fillet weld carries, and the leg size | Fillet Weld Strength Calculator |
| Base plate thickness, and whether the concrete crushes | Base Plate Design Calculator |
| Bolt shear against bearing, and which governs | Bolt Capacity Calculator |
| Need wind load before picking a member | Wind Load Calculator |
| Only need the section weight and weld consumable | Section Steel Weight Calculator |
Where this group goes wrong
- Sizing a weld on the leg rather than the throat. A 6 mm leg has a 4.2 mm throat, so capacity falls from 269 kN to 188 kN — a 43% over-prediction. The weld resists shear across its throat, never across the leg, and this still slips through drawing reviews.
- Taking an effective length factor of 0.5 for fixed ends. The theory is right, but real fixity needs a stiff base plate, a stiff foundation and no bolt slip, which is rarely achieved. Using 0.5 over-predicts capacity fourfold; 0.7 to 0.8 is what practice allows, and that difference already eats half the margin.
- Choosing a beam section on strength. At 6 m and 20 kN/m the strength check needs 360 cm³ of section modulus while L/360 needs 9643 cm⁴ of inertia, two sizes apart. The lighter section installed is felt underfoot and cracks the finishes above.
- Thickening a base plate when the area is short. Pressure is P/(B N), so doubling the area halves it and cuts the required thickness to 71%, whereas doubling thickness costs money squared. Always enlarge first, then compute thickness.
- Using the Euler load as capacity. Euler omits initial bow, residual stress and eccentricity, so it always over-predicts — HEB200 at 4 m pinned gives 7379 kN against 1548 kN real, a factor of 4.8. Applied directly, a column collapses at a third of the design load.