Commercial Real Estate, Workplace Space Planning & BOMA Standards
BOMA Rentable vs Usable Square Feet, Load & Loss Factor Formula
Calculate ANSI/BOMA Z65.1 Billed Rentable Square Feet RSF = USF * R/U_Load_Ratio, Equivalent Market Loss Factor (RSF - USF) / RSF, Annual Base Rent, and True Effective Cost per Carpetable Usable Square Foot.
Never confuse Add-On Load Factor with Loss Factor when comparing commercial office buildings!
Corporate real estate teams comparing two office towers at "$45.00/RSF" frequently overpay by 5%–10% because tenants occupy Usable Square Feet (USF—actual private carpetable workspace inside suite walls) while landlords bill Rentable Square Feet (RSF = USF * BOMA_R/U_Ratio, allocating shared elevator lobbies, restrooms, mechanical rooms, and amenities)! Watch the classic Add-On vs Loss Factor trap: a 20% BOMA Load Factor (R/U Ratio = 1.20) adds 20% onto USF, which equals a 16.67% Loss Factor ((RSF - USF) / RSF = 0.20 / 1.20), whereas a 20% REBNY Loss Factor divides USF by (1 - 0.20) = 1.25x R/U Ratio! Comparing competing proposals on Effective Rent per Carpetable USF = Quoted_Rent_RSF * R/U_Ratio puts every building on an apples-to-apples footing!
Verify on a Multi-Tenant Office Floor—Carpetable_Usable_Area USF = 16,000 sq ft (B2), BOMA_R/U_Load_Ratio = 1.20 (20% core/common add-on, B3), and Quoted_Rent = $45.00/RSF (B4): Billed Rentable Area is 16,000 * 1.20 = 19,200.00 RSF (E2); Equivalent Loss Factor is (19,200 - 16,000) / 19,200 = 0.1667 (16.67% in E3); Annual Gross Rent is 19,200 * $45 = $864,000.00 (E4); and True Effective Cost per Carpetable USF is $864,000 / 16,000 = $54.00/USF (E5)!
| BOMA Z65.1 Space Metric (16,000 USF, 1.20 R/U Load Ratio, $45.00/RSF) | Formula | Verified Output |
|---|---|---|
| Billed Rentable Area (RSF) | Usable_USF * BOMA_RU_Load_Ratio | 19,200.00 RSF (20,000 @ 1.25x) |
| Equivalent Building Loss Factor | (Rentable_RSF - Usable_USF) / RSF | 0.1667 (0.2000 @ 1.25x Load) |
| Annual Base Lease Rent ($) | Rentable_RSF * Quoted_Rent_RSF | $864,000.00/yr |
| Effective Cost per Carpetable USF | Annual_Rent / Usable_USF | $54.00/USF ($56.25 @ 1.25x) |
BOMA True Effective Rent per Usable Square Foot Formula
Validate Usable_USF > 0, realistic BOMA R/U Load Ratio 1.00 <= R/U < 2.00, and Quoted_Rent_RSF > 0!
=LET(us_f, B2, ru_l, B3, qt_r, B4, IF(OR(us_f <= 0, ru_l < 1, ru_l >= 2, qt_r <= 0), "Invalid BOMA Lease Area", ROUND((us_f * ru_l * qt_r) / us_f, 2)))20% Loss-Factor Tower Comparison (Set BOMA R/U Ratio = 1.25)
Test a competing tower with a 20% Loss Factor (B3 = 1.25 R/U Load Ratio) at the same $45/RSF face rate: Billed RSF E2 jumps to 20,000 RSF, Loss Factor E3 hits 0.2000, and Effective Cost E5 rises to $56.25/USF (+$36,000/yr for identical desk capacity)!
=IF(ISTEXT(E2), E2, ROUND((E2 - B2) / E2, 4))Try the example
Use the original values or change them to test your understanding.