SettingsSettings for this calculationUS
The distance between standards along the face — the length of platform the load sits on.
Measure between the uprights at each end of the bay. A duty rating is a load per unit of platform area, so the same people and materials on a shorter bay make a higher figure — which is why heavier-duty scaffolds are built with shorter bays.
The boarded width of the platform, across the scaffold.
The width of decking people and materials stand on, not the width of the frame including a guardrail post. A wider platform spreads the same load thinner.
How many people will be on this bay at the same time.
Count the most people who will stand on the bay together, including anyone passing along it. Zero leaves only the materials.
An allowance you choose — the ratings describe the platform, not the person.
Neither OSHA's ratings nor BS EN 12811-1's classes say what a person weighs; they rate the platform. 100 kg (about 220 lb) covers most people carrying hand tools. Use more for someone carrying heavy tools or kit.
Everything else on the bay — blocks, mortar, tools, a mixer.
The weight of materials and equipment stored or used on this bay at the same time as the people. A pallet or a stack puts most of its weight on a small area of the boards, which a uniform rating does not describe — the result here is the average over the whole bay.
Load spread over the bay
31.4 psf averaged over the bay
The load spread evenly over this bay is above OSHA's light-duty rating and within medium duty, and above class 2 of BS EN 12811-1 and within class 3. A rating describes a load spread evenly over the whole platform: a pallet or a stack puts far more than the average on the boards beneath it, and both systems add concentrated and partial-area loads a uniform figure does not show, so a figure within a rating is not a finding that the bay can carry its load as placed.
- Total weight on the bay
- 880 lb
- Platform area of the bay
- 28 ft²
- OSHA light-duty rating
- 25 psf
- OSHA medium-duty rating
- 50 psf
- OSHA heavy-duty rating
- 75 psf
- BS EN 12811-1 class 3, the lowest at or above this load
- 41.77 psf
- Four times the load on the bay, which each component must support
- 3,520 lb
They open the calculator with your figures already in it
Scaffold Platform Load and Duty Rating Calculator: 31.43 psf averaged over the bay — shown in imperial, US market. The link sets both, so the result they see is the one on your screen.
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How this was calculated
Formula source(s)
- Appendix A to Subpart L of 29 CFR Part 1926 (non-mandatory): light-duty scaffolds are rated at 25, medium-duty at 50 and heavy-duty at 75 pounds per square foot (1.2, 2.4 and 3.6 kN/m²) applied uniformly over the entire span area
- BS EN 12811-1:2003, Temporary works equipment — Scaffolds: six service load classes with uniformly distributed loads of 0.75, 1.5, 2.0, 3.0, 4.5 and 6.0 kN/m² (about 16, 31, 42, 63, 94 and 125 psf), each with concentrated and partial-area loads as well
- 29 CFR 1926.451(a)(1): each scaffold and scaffold component shall be capable of supporting, without failure, its own weight and at least 4 times the maximum intended load applied or transmitted to it
Inputs used
- Bay Length
- 7 ft
- Platform Width
- 4 ft
- People Working on the Bay
- 2
- Weight of Each Person, With Tools
- 220 lb
- Materials on the Bay
- 440 lb
Intermediate steps
- Total weight on the bay
- 880 lb
- Platform area of the bay
- 28 ft²
- OSHA light-duty rating
- 25 psf
- OSHA medium-duty rating
- 50 psf
- OSHA heavy-duty rating
- 75 psf
- BS EN 12811-1 class 3, the lowest at or above this load
- 41.77 psf
- Four times the load on the bay, which each component must support
- 3,520 lb
Confidence note: The load spread evenly over this bay is above OSHA's light-duty rating and within medium duty, and above class 2 of BS EN 12811-1 and within class 3. A rating describes a load spread evenly over the whole platform: a pallet or a stack puts far more than the average on the boards beneath it, and both systems add concentrated and partial-area loads a uniform figure does not show, so a figure within a rating is not a finding that the bay can carry its load as placed.
What this calculation does not cover
- It compares the load averaged over the bay. BS EN 12811-1 sets concentrated and partial-area loads for every class as well as the uniform one, and stacked materials are judged against those, which this page does not do.
- It takes one bay. The loads on the lifts above and below, and the weight of the scaffold itself, all reach the standards, the base plates and the ties.
- The weight of a person is your allowance, not a figure either rule gives.
- OSHA's duty ratings come from Appendix A to Subpart L, which is non-mandatory. The rule itself is that each component supports its own weight and at least four times the maximum intended load.
Computed in your browser — nothing you enter is uploaded. Presented in US customary units and US trade terminology. Where a formula follows a published standard, that standard and its edition are cited beside it on this page; where none governs, the page says so. Local amendments override model codes — verify against the code in force where you build.
Sources checked 2026-09-21 · v1.0.0
Regulatory standards & verification citations3
- Appendix A to Subpart L of 29 CFR Part 1926 (non-mandatory): light-duty scaffolds are rated at 25, medium-duty at 50 and heavy-duty at 75 pounds per square foot (1.2, 2.4 and 3.6 kN/m²) applied uniformly over the entire span area
- BS EN 12811-1:2003, Temporary works equipment — Scaffolds: six service load classes with uniformly distributed loads of 0.75, 1.5, 2.0, 3.0, 4.5 and 6.0 kN/m² (about 16, 31, 42, 63, 94 and 125 psf), each with concentrated and partial-area loads as well
- 29 CFR 1926.451(a)(1): each scaffold and scaffold component shall be capable of supporting, without failure, its own weight and at least 4 times the maximum intended load applied or transmitted to it
Which documents these citations point at
Standards referenced: BS EN 12811-1 (European Committee for Standardization, as published in the UK by BSI, European (EN)).
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