Calculator Inputs
Enter project settings first, then define each story or roof level below.
Formula Used
The calculator evaluates each story separately, then sums all participating levels to obtain the building seismic weight.
In imperial units, the conversion factor is 0.001 because area multiplied by psf gives pounds, and pounds are converted to kips. In metric units, no load conversion is needed when using m² and kN/m².
How to Use This Calculator
- Select the preferred unit system and enter the project details.
- Set the default participation percentages for live, roof live, and snow loads.
- Fill in each story card with area, load intensities, and fixed additional loads.
- Add extra story cards for mezzanines, basements, roofs, or penthouses.
- Submit the form to view the result section above the input form.
- Use the CSV or PDF buttons to export the calculated story summary.
Example Data Table
Example below uses imperial units and shows one possible office building breakdown.
| Story | Area (ft²) | Dead (psf) | Super Dead (psf) | Partitions (psf) | Live (psf) | Live % | Roof Live (psf) | Roof % | Snow (psf) | Snow % | Equipment (kips) | Cladding (kips) | Misc. (kips) | Story Weight (kips) |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| Roof | 6000 | 35 | 12 | 0 | 0 | 0 | 20 | 20 | 15 | 20 | 8 | 5 | 1 | 338.00 |
| Level 2 | 6000 | 48 | 15 | 10 | 50 | 25 | 0 | 0 | 0 | 0 | 10 | 6 | 3 | 532.00 |
| Level 1 | 6000 | 50 | 15 | 10 | 50 | 25 | 0 | 0 | 0 | 0 | 12 | 6 | 2 | 545.00 |
| Total Example Seismic Weight | 1415.00 | |||||||||||||
Frequently Asked Questions
1) What is seismic weight?
Seismic weight is the portion of building weight used for earthquake design. It usually includes dead loads, fixed equipment, partitions, and selected portions of variable loads.
2) Why is live load reduced?
Many codes include only part of the unreduced live load because it is unlikely that every floor reaches maximum occupancy during an earthquake event.
3) Should roof live load always be included?
Not always. Many standards include only a percentage of roof live load, and some cases allow exclusions. Always verify the governing code.
4) Are partitions part of seismic weight?
Yes, movable or assumed partition loads are often included when required by code. This calculator lets you add them as a floor intensity.
5) Does the importance factor change seismic weight?
No. The importance factor affects later design checks in many methods, but it does not usually change the building seismic weight itself.
6) What units should equipment and cladding use?
Enter those as direct story weights. Use kips in imperial mode and kN in metric mode for consistent total results.
7) Can I use this for irregular buildings?
Yes, for preliminary or documented load aggregation. However, irregular structures may still require more detailed modeling and code-specific review.
8) Is this calculator a substitute for code checks?
No. It is a structured calculation tool. Final seismic design still requires engineering judgment, code interpretation, and full lateral analysis.