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Load Factor Calculator

Office load factor stacks two layers — floor common area (corridors, restrooms, lobby on the tenant's floor) and building common area (main lobby, mechanical rooms, fire stairs). This calculator computes both and the total load factor that converts usable SF into rentable SF.

Usable SF on floor

Floor common areas (corridors, lobby)

Building common areas (main lobby, mech)

Total load factor

1.172

Total add-on %

17.22%

Floor load factor

1.122

Building load factor

1.045

Rentable SF on floor

20,200

Rentable SF (fully loaded)

21,100

How the math works

Load factors stack — floor load (usable + floor common) and building load (floor RSF + building common) multiply to the total load factor. A 1.12 floor × 1.05 building = 1.176 total load. Single-tenant floors skip the floor load entirely.

Tenants on small partial floors pay both loads. Tenants on full floors pay only the building load. That's why partial floors often price at slightly higher effective $/USF despite identical headline $/RSF.

Editorial noteMaintained by EveryCalc - Reviewed June 2026

EveryCalc calculators are designed for fast, practical estimates with transparent inputs and no required account. We use plain formulas, visible assumptions, and related tools so visitors can check the result from more than one angle.

Results are informational only. For financial, tax, legal, medical, construction, or other high-impact decisions, verify the output against primary sources or a qualified professional.

Learn more about our review process on the EveryCalc methodology page.

How this calculator works

What this page estimates

This Load Factor Calculator is built to give a quick, browser-based estimate for load factor. Office load factor stacks two layers — floor common area (corridors, restrooms, lobby on the tenant's floor) and building common area (main lobby, mechanical rooms, fire stairs). This calculator computes both and the total load factor that converts usable SF into rentable SF. The inputs stay on the page during normal use, and the result should be treated as an estimate for planning, comparison, or education rather than professional advice.

Calculation approach

The calculator applies the standard relationship implied by the inputs, then formats the answer so it can be checked and reused. For finance tools, the most important step is using consistent units, rates, time periods, and assumptions before comparing the result with another calculator or outside quote.

Example workflow

For example, start with a realistic value you already know, change one input at a time, and watch how the answer moves. That makes it easier to tell whether the result is being driven by the main amount, the rate, the time period, or a unit conversion.

Practical checks

Use current, real-world numbers when the result affects money, health, tax, or legal decisions.
Run a low, base, and high case when the inputs are estimates.
Check the related calculators below when the next decision depends on a different assumption.

How to interpret the load factor result

Best use

Use the result as a planning number for comparing payments, rates, returns, tax reserves, or cash-flow choices before you request a quote or make a commitment.

Cross-check

Compare the answer with the contract, lender estimate, tax form, brokerage statement, payroll record, or invoice that will control the real-world outcome.

Watch for

Do not rely on a single optimistic rate, return, or fee assumption. Money pages work best when you run low, base, and high cases and keep professional advice separate from the estimate.

This page belongs to the Finance calculator library, so the answer should be read in the context of the decision you are modeling rather than as a universal rule.

Before relying on this load factor estimate

Most calculator mistakes come from the inputs, not the arithmetic. Use this short audit before you reuse the answer in a spreadsheet, quote, application, or important conversation.

Confirm source numbers

Match balances, rates, fees, taxes, income, and payment dates against the lender quote, payroll record, tax form, statement, invoice, or contract.

Separate cash flow from total cost

A lower monthly payment can still cost more over time if fees, interest, taxes, or a longer term are hidden in the structure.

Run conservative cases

Test at least one higher-cost or lower-return case before using the output for a purchase, refinance, investment, loan, or tax decision.

Rerun this page when the rate, price, term, fee, tax rule, income, expense, or expected holding period changes.

How to Use

Enter usable SF inside the tenant premises.
Enter floor common SF (corridors, elevator lobby, restrooms on that floor).
Enter building common SF (main lobby, mechanical, pro-rata).
Read the stacked load factors.

Frequently Asked Questions

Floor load vs building load?

Floor load applies to partial-floor tenants. Building load is everyone's share of the main lobby, fire stairs, mechanical. Full-floor tenants avoid the floor load because they 'own' the whole floor's common areas.

BOMA 2017 changes?

BOMA 2017 aligned with international IPMS standards — slightly different treatment of mechanical and service areas. Most Class A buildings have re-measured under 2017 standards by now.

How does this affect rent negotiation?

Tenants should quote effective rent per USF, not RSF, when comparing buildings. A 1.12 load building at $32/RSF is $35.84/USF; a 1.18 load building at $31/RSF is $36.58/USF — the 'cheaper' building is actually more expensive.