Seismic Base Shear Calculator

Calculate seismic base shear using the ASCE 7 equivalent lateral force procedure: V = Cs × W.

SDS (Short-Period Spectral Acceleration)

Low seismicity: 0.1–0.3g; moderate: 0.3–0.7g; high (California): 0.7–2.0g per ASCE 7

SD1 (1-Second Spectral Acceleration)

Building Period (T)

Response Modification Factor (R)

ASCE 7 Table 12.2-1: Special MRF = 8; Ordinary CBF = 3.25; Concrete SW = 5; Wood SW = 6.5

Importance Factor (Ie)

ASCE 7 Table 1.5-2: Risk Cat I–II = 1.0; Risk Cat III (schools) = 1.25; Risk Cat IV = 1.5

Seismic Weight (W)

Tab to move between fields

Seismic Coefficient (Cs)

0.16

Base Shear (V)

8,000 kN

Overturning Moment118,685.86 kN·m

Total Story Forces8,000 kN

How to Use This Calculator

Obtain SDS and SD1 values from USGS seismic hazard maps for your site location.
Enter the building fundamental period T, the response modification factor R, and importance factor Ie.
Input the total seismic weight W in kN (dead load plus applicable live load fractions).
Review the Seismic Coefficient Cs and the Base Shear V in kN.
Use the Overturning Moment output to size foundation elements and lateral force-resisting systems.

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