How thick is 9 gauge galvanised steel?

9 gauge galvanised steel is 0.1532 in thick, which is 3.891 mm. A square foot weighs 6.25 lb (30.52 kg/m²).

What is 9 gauge galvanised steel in mm?

3.891 mm. The gauge number is an index into the galvanized-MSG system rather than a measurement, so it converts to a fixed thickness rather than a round metric figure.

Why is 9 gauge a different thickness in other materials?

Because each material is indexed on its own gauge system. At 9 gauge: Aluminium 0.1144 in (B&S), Galvanized 0.1532 in (galvanized-MSG), Steel 0.1495 in (MSG), US Standard 0.1563 in (USG). The number is a position in a series, not a thickness, so 3 other readings of "9 gauge" are all equally correct.

Sheet metal · Galvanized Steel · galvanized-MSG

9 Gauge Galvanised Steel Thickness in Inches and Millimetres

https://shopmath.org/gauges/galvanized/9 · data verified August 1, 2026

9 gauge galvanised steel sheet is 0.1532 in thick — 3.891 mm. A square foot weighs 6.25 lb (30.52 kg/m²). The gauge number indexes the galvanized-MSG system, so the same number is a different thickness in another material — the comparison is below. Thicknesses are nominal, before mill tolerance.

Gauge: 9 ga
Material: Galvanized Steel
Inch: 0.1532
mm: 3.891
System: galvanized-MSG

9 Gauge Galvanised Steel · nominal thickness

0.1532 in

Millimetre: 3.891mm
Weight: 6.25lb/ft²
Weight: 30.52kg/m²

Nominal thickness on the galvanized-MSG system. Gauge numbers are material-specific — "9 gauge" on its own does not name a thickness.

9 Gauge Galvanised Steel Sheet Thickness

9 Gauge Galvanised Steel is defined by the MSG plus zinc coating allowance, not by a measurement — the gauge number is an index into that system, which is why the same number means a different thickness in another material.

9 Gauge Galvanised Steel — thickness and weight
Property	Value
Thickness, decimal inch	0.1532 in
Thickness, millimetre	3.891 mm
Weight per square foot	6.25 lb/ft²
Weight per square metre	30.52 kg/m²
Gauge system	galvanized-MSG

Nominal thickness. Mill tolerance on sheet is typically a few thousandths of an inch either way and varies with width and process; measure the stock when the fit matters.

9 Gauge Thickness in Every Other Sheet Material

Gauge 9 spans 0.1144 in to 0.1563 in depending on the material, because each material is indexed on a different gauge system. Ordering sheet by gauge without naming the material is how the wrong thickness arrives.

Thickness of 9 gauge sheet across materials
Property	Property	Thickness
Material	Gauge system	in	mm
Sheet Aluminium	B&S	0.1144	2.906
Galvanized Steel	galvanized-MSG	0.1532	3.891
Sheet Steel	MSG	0.1495	3.796
U.S. Standard Gauge	USG	0.1563	3.969

Steel uses the Manufacturers' Standard Gauge, galvanised adds a zinc-coating allowance to the steel thickness, aluminium and other non-ferrous sheet use the Brown & Sharpe geometric series, and U.S. Standard is the 1893 statute on a wrought-iron basis.

Gauges Either Side of 9 Gauge Galvanised Steel

A higher gauge number is thinner sheet. The steps are not equal — the gauge systems are geometric, so the difference between two gauges shrinks as the sheet gets thinner.

Galvanized Steel gauges adjacent to 9 gauge
Property	Thickness
Gauge	in	mm
9 ga	0.1532	3.891
10 ga	0.1382	3.511
11 ga	0.1233	3.132

Sources and Method for 9 Gauge Galvanised Steel Thickness

9 Gauge Galvanised Steel thicknesscomputed

15 U.S.C. 206 (Act of Mar. 3, 1893, ch. 221, 27 Stat. 746) — U.S. Standard Gauge for sheet and plate iron and steel; 15 U.S.C. 206 statutory weights; MSG (41.82 lb/ft2 per inch), galvanized zinc allowance, and Brown & Sharpe formula per docs/research/data-sourcing.md §3.7

Verified against Wikipedia Sheet metal, Standard sheet metal gauges table (CC BY-SA 4.0) — 137/137 checks passed at 0.05 mil

Computed from the standard's formulas, then checked against published tables.

Formula

Weight per square foot, sheet steel

lb/ft²  =  thickness (in) × 41.82

  0.1532 × 41.82  =  6.25 lb/ft²

41.82 lb/ft² per inch of thickness is the Manufacturers' Standard Gauge basis for steel. The U.S. Standard Gauge of 1893 uses a wrought-iron basis of 40 lb/ft² per inch, which is why the two systems differ.

Assumptions

Thicknesses are nominal. Mill tolerance varies with width, process and material and is not part of the gauge definition.
Gauge is an index into a material-specific system, not a unit. A gauge number without a material is ambiguous by construction.
Dataset scope: EXCLUDED: stainless steel (genuinely ambiguous convention, only one source in hand), zinc, copper, brass, steel tube wall.

Data last verified

August 1, 2026

How this data is built and checked →

How to Cite This 9 Gauge Galvanised Steel Reference

Citation

ShopMath. "9 Gauge Galvanised Steel Thickness in Inches and Millimetres." ShopMath, verified August 1, 2026, https://shopmath.org/gauges/galvanized/9

BibTeX

@misc{shopmath-gauges-galvanized-9,
  title        = {9 Gauge Galvanised Steel Thickness in Inches and Millimetres},
  author       = {{ShopMath}},
  year         = {2026},
  howpublished = {\url{https://shopmath.org/gauges/galvanized/9}},
  note         = {Data verified 2026-08-01}
}

Permanent URL

https://shopmath.org/gauges/galvanized/9

Common Questions About 9 Gauge Galvanised Steel

How thick is 9 gauge galvanised steel?: 9 gauge galvanised steel is 0.1532 in thick, which is 3.891 mm. A square foot weighs 6.25 lb (30.52 kg/m²).
What is 9 gauge galvanised steel in mm?: 3.891 mm. The gauge number is an index into the galvanized-MSG system rather than a measurement, so it converts to a fixed thickness rather than a round metric figure.
Why is 9 gauge a different thickness in other materials?: Because each material is indexed on its own gauge system. At 9 gauge: Aluminium 0.1144 in (B&S), Galvanized 0.1532 in (galvanized-MSG), Steel 0.1495 in (MSG), US Standard 0.1563 in (USG). The number is a position in a series, not a thickness, so 3 other readings of "9 gauge" are all equally correct.

All 24 galvanized gauges · Sheet metal gauge chart · Every gauge system