Measuring before you order pans
A pan fabricator cuts to your numbers, not to a field guess. Get these four measurements right before you request a quote.
Total rise, floor to floor
Plumb down from the finished top floor to the finished bottom floor, same as any stair. Pan stairs are almost always commercial egress stairs, so this number gets checked against IBC limits, not IRC.
Clear width between rails or walls
Measure the usable width the stair needs to carry — this sets both the pan width and, directly, the concrete fill volume per tread. Confirm your occupant-load-driven minimum with your code official before finalizing.
Decide fill type before you spec pans
Concrete-filled is the traditional egress-stair standard. An unfilled pan with a bar-grating or checkered-plate insert skips the concrete entirely — pick this in Advanced before reading the concrete outputs.
Confirm gauge and fill depth with the fabricator
This calculator estimates steel weight from a gauge you select, but the actual required gauge is an engineering call based on pan span and design load — treat the weight and area figures as planning estimates, not a stamped spec.
The formulas behind every result
Nothing on this page is a black box. Here's exactly what runs when you change a number.
Step Count
Total rise divided by your target riser height, rounded to the nearest whole step — you can't fabricate a fractional pan.
Actual Riser Height
The rounding above means your real riser is rarely the exact target. Every riser pan gets cut to this height, uniformly.
Tread Depth (2R+T rule)
The standard comfort formula, floored at the 11" IBC commercial minimum. At the 7" IBC max riser this formula lands exactly on 11" — see the worked example.
Concrete Fill per Pan
Width times the pan's plan area (tread depth plus nosing overhang) times fill depth, converted to cubic feet — the volume poured into one tread pan.
Total Concrete, with Waste
One pan per tread (not per riser — the top and bottom floors aren't pans), plus any landing pan, inflated by your waste factor for field spill and over-pour.
Steel Pan Weight
Total pan sheet area (tread face plus riser face, per pan) times gauge thickness times the standard density of structural steel.
Walking through a 126" commercial flight
Same formulas, filled in step by step, for a 126" (10'-6") rise, 48" wide commercial stair at IBC-max riser — the default this calculator loads with once you set those values.
Step count and actual riser
126" total rise at a 7" target: 126 ÷ 7 = 18 steps exactly, so the actual riser stays at a clean 7.00" — no rounding remainder to absorb.
Tread depth — where the rule meets the code minimum
2R+T rule: 25 − (2 × 7.00) = 11.00", which happens to land exactly on the IBC 11" minimum. This isn't a coincidence you'll see often: because IBC's commercial riser cap (7") and the 2R+T comfort formula are already tuned to agree at the maximum riser, pushing riser to its legal limit is the one case where the comfort rule and the code floor produce the identical number instead of one overriding the other.
Concrete fill per pan
Plan area is tread plus nosing: 11.00" + 1.25" = 12.25". At 48" width and a 1.5" fill depth: 48 × 12.25 × 1.5 = 882 in³ = 0.51 ft³ per pan.
Total concrete, with waste
17 tread pans (18 steps minus the top floor) at 0.51 ft³ = 8.68 ft³ = 0.32 yd³. Add a 10% waste factor: ≈0.35 yd³ — enough that most jobs this size still hand-mix or use bagged concrete rather than ordering a truck.
Steel pan weight
Per pan, tread face (48 × 12.25 = 588 in²) plus riser face (48 × 7 = 336 in²) totals 924 in² ≈ 6.42 ft². At 12-gauge (0.1046") and 490 lb/ft³: 6.42 × (0.1046 ÷ 12) × 490 ≈ 27.5 lb per pan, roughly 467 lb across all 17 pans, before stringers, rails or landing.
Push the riser target below 7" and the tread floor stops binding — the comfort formula takes back over and tread depth grows past 11", which increases both concrete volume and steel area per pan. That trade-off is why most utilitarian commercial pan stairs run at or near the 7"/11" limit rather than a more generous residential-feeling ratio.
Sheet steel gauge, in decimal inches
Manufacturers' Standard Gauge for steel sheet — what this calculator's Pan Steel Gauge dropdown uses to convert your selection into a thickness for the weight estimate.
| Gauge | Thickness (in) | Thickness (mm) | Typical pan use |
|---|---|---|---|
| 10 ga | 0.1345" | 3.42 mm | Wider spans, heavier design loadVERIFY |
| 11 ga | 0.1233" | 3.13 mm | Mid-range spansVERIFY |
| 12 ga | 0.1046" | 2.66 mm | Common default for standard pan spansVERIFY |
| 14 ga | 0.0747" | 1.90 mm | Lighter-duty or short-span pansVERIFY |
| 16 ga | 0.0598" | 1.52 mm | Minimum seen in field references, short spans onlyVERIFY |
Gauge selection is an engineering decision driven by pan span (distance between stringers) and design load — it is not a fixed code table. The "typical use" column is a general field pattern, not a substitute for your fabricator's stamped calculation.
IBC commercial stair code, quick reference
Pan stairs are almost always egress stairs in commercial or institutional buildings, so this calculator checks results against IBC — not the residential IRC numbers used on wood-stair pages.
| Element | Commercial (IBC) | Residential (IRC) |
|---|---|---|
| Max riser height | 7" | 7.75" |
| Min tread depth | 11" | 10" |
| Riser/tread variance across a flight | 3/8" | 3/8" |
| Min headroom | 80" | 80" |
| Min clear width | 44" (36" if occupant load <50) | 36" |
| Max flight rise before landing | 144" (12')VERIFY | 147" (12'-3") |
Reference only — always confirm against your local jurisdiction's adopted code edition before ordering pans. Nosing profile, stringer attachment and handrail requirements are covered separately in the fabrication section below.
Concrete fill, nosing detail & fabrication notes
A pan order that gets the riser and tread right can still come back wrong on the shop floor over these three details.
Why fill depth is typically 1.5"
Field-poured concrete fill in a stair pan is commonly around 1.5" deep, set flush with the nosing return. It's a fabrication convention driven by pan forming and finish thickness, not a hard code minimum — confirm the exact depth on your project's stair detail before ordering.
Nosing overhang and return
The nosing lip typically projects no more than about 1.5" past the riser face, with the return (the small vertical lip under the nosing) sitting flush with the top of the concrete fill. Get this detail wrong and the poured fill either shows a gap or overhangs the steel edge.
Filled vs. unfilled pans
Unfilled pans skip the field pour entirely and instead accept a bar-grating, checkered-plate, or abrasive-nosing insert — common on roof access and temporary construction stairs where wet-pour scheduling isn't practical. Switch Fill Type to Unfilled and the concrete outputs above go to zero.
Stringer spacing still governs gauge
This calculator's steel weight is only as good as the gauge you pick, and pan span is set by stringer spacing, not by anything entered here. For the spacing math itself, use the dedicated Stringer Spacing Calculator before locking in a gauge.
This section covers fabrication-stage planning, not a stamped structural design. Pan gauge, weld pattern and stringer spacing on any commercial egress stair need engineer sign-off regardless of what this calculator shows.
Common mistakes when ordering metal pan stairs
Most pan re-orders and field rework trace back to one of these five planning errors, not to bad fabrication.
Using IRC riser/tread limits instead of IBC
Pan stairs are commercial egress stairs almost by definition. Designing to the residential 7.75"/10" numbers instead of the commercial 7"/11" limits is a common and easily avoidable code failure.
Guessing fill depth instead of checking the detail
Fill depth is a fabrication convention, not a fixed number — ordering pans sized for a 1.5" pour when the project detail calls for 2" leaves the finished tread proud of the nosing or short of it.
Picking gauge by habit, not by span
A gauge that worked on a 3' wide stair can be undersized on a 5' wide one at the same rise — pan span, not stair width alone, drives the required thickness. Confirm with the fabricator's engineer, not a rule of thumb.
Forgetting the landing pan in the concrete take-off
Landing pans get filled to the same depth as tread pans but are easy to leave out of a quick volume estimate — a mid-size landing can add 20–30% to the total pour.
Ordering concrete for a truck when bags will do
Most single-flight pan fills land well under half a cubic yard. Ordering ready-mix delivery for a volume that small usually costs more than bagged concrete mixed on site — check the total before you call a supplier.
When to use a metal stair pan calculator
Pan stair planning shows up wherever a steel-framed egress stair needs a durable, code-legal tread surface.
Commercial Egress Stairs
Sizing pans and fill for a code-required exit stair in an office or retail building.
Industrial & Plant Access
Rugged steel stairs for equipment platforms and mezzanine access.
Institutional Buildings
Schools, hospitals and government buildings where IBC governs every stair.
Fabricator Quoting
Getting a fast steel-weight and concrete-volume estimate before a shop drawing is finalized.
Concrete Take-off
Pulling a quick cubic-yard number for a bid, before ordering bagged or ready-mix concrete.
Roof & Maintenance Access
Comparing an unfilled grating-insert pan against a full concrete fill for a low-traffic access stair.