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Declared arithmeticUser-supplied inputsPreliminary

Structural Load
Calculator

Multiply a repeated tributary area by user-supplied permanent and imposed area loads, then optionally apply user-supplied weighting factors.

Who it's for: structural engineers summing tributary loads at schematic design or construction documents.

Bounded scope: this worksheet does not select loads, load combinations, reduction factors, standards, or structural members. A qualified structural engineer must establish all project criteria and perform the design.

Published benchmarks

Minimum uniformly distributed live loads from IBC 2021 Table 1607.1. Confirm against the edition adopted in your jurisdiction.

BenchmarkValueUnitEditionScopeSource
Residential, private rooms and corridors40psfIBC 2021Model code, USIBC 2021 Table 1607.1 (Oregon OSSC 2022 viewer)Reference only — enter a verified rate separately
Office50psfIBC 2021Model code, USIBC 2021 Table 1607.1 (Oregon OSSC 2022 viewer)Reference only — enter a verified rate separately
Corridors above first floor (office)80psfIBC 2021Model code, USIBC 2021 Table 1607.1 (Oregon OSSC 2022 viewer)Reference only — enter a verified rate separately
Assembly, fixed seats60psfIBC 2021Model code, USIBC 2021 Table 1607.1 (Oregon OSSC 2022 viewer)Reference only — enter a verified rate separately
Assembly, movable seats100psfIBC 2021Model code, USIBC 2021 Table 1607.1 (Oregon OSSC 2022 viewer)Reference only — enter a verified rate separately
Assembly, lobbies100psfIBC 2021Model code, USIBC 2021 Table 1607.1 (Oregon OSSC 2022 viewer)Reference only — enter a verified rate separately
Retail, first floor100psfIBC 2021Model code, USIBC 2021 Table 1607.1 (Oregon OSSC 2022 viewer)Reference only — enter a verified rate separately
Retail, upper floors75psfIBC 2021Model code, USIBC 2021 Table 1607.1 (Oregon OSSC 2022 viewer)Reference only — enter a verified rate separately
Storage, light125psfIBC 2021Model code, USIBC 2021 Table 1607.1 (Oregon OSSC 2022 viewer)Reference only — enter a verified rate separately
Storage, heavy250psfIBC 2021Model code, USIBC 2021 Table 1607.1 (Oregon OSSC 2022 viewer)Reference only — enter a verified rate separately
Roof, ordinary flat, pitched or curved (not occupiable)20psfIBC 2021Model code, USIBC 2021 Table 1607.1 (Oregon OSSC 2022 viewer)Reference only — enter a verified rate separately
Roof, used for assembly100psfIBC 2021Model code, USIBC 2021 Table 1607.1 (Oregon OSSC 2022 viewer)Reference only — enter a verified rate separately

Each button selects the stated displayed value, not a typical rate, statistical confidence interval, or recommendation. Inequality bounds are reference-only. Figures are as published on the linked page; check edition, unit, scope and what the rate includes before using one. When a base-date field is present, enter its verified date yourself; a publication year is not a benchmark base month.

Area-load arithmetic
Values must use a consistent unit system

How to use this calculator

1
Enter one tributary area
Use the area supported by the point or line being studied.
2
Enter repeated levels
Use this shortcut only when the same entered area loads and tributary area repeat on every included level.
3
Enter project-defined loads
Permanent and imposed area loads must come from the project basis; this worksheet supplies no presets.
4
Enter project-defined factors
Use factors from the combination selected by the responsible engineer. Enter 1 and 1 for an unfactored sum.

The formula

Permanent contribution = tributary area × repeated levels × permanent area load.
Imposed contribution = tributary area × repeated levels × imposed area load.
Weighted total = permanent contribution × entered permanent factor + imposed contribution × entered imposed factor.

Worked example

Example
For an area of 25, five repeated levels, permanent load 4.5, imposed load 2.4, and user-entered factors 1.2 and 1.6: permanent contribution = 562.5, imposed contribution = 300, unfactored total = 862.5, and weighted total = 1,155.

When this estimate will be off

  • No occupancy or load values are supplied; all project loads must be established independently.
  • No standard, adopted edition, governing load combination, load reduction, or exceptional load case is selected.
  • Repeated levels must share the same tributary area and entered loads; otherwise calculate levels separately.
  • No member demand, strength, stability, deflection, connection, reinforcement, foundation, or adequacy check is performed.

Frequently asked questions

A common mistake: No occupancy or load values are supplied; all project loads must be established independently.

No. It performs arithmetic on values and factors you enter. It does not determine which loads, combinations, reductions, or standards govern.

No. The former preliminary column-sizing output was removed because the route lacked the information required for a member design.

Use one consistent unit system. If area is m² and area load is kN/m², the totals are kN. The worksheet does not detect mixed units.

Sources

  • Declared arithmetic method — uses only the user-entered area, repeated levels, area loads, and factors
  • Project structural criteria — must supply the loads, combinations, units, and applicability outside this worksheet

This free Structural Load Calculator is built and maintained by DataDrivenAEC, using the relevant codes and standards. It does not substitute for professional judgment.