Skillet & Stove

What Do the Numbers on Cast Iron Mean?

There are usually two numbers on the bottom of an old pan and they do completely different jobs. One is a size in a legacy system that has nothing to do with inches; the other identifies the mould it was cast from.

By Stephen V.Last updated How we pick

How this is funded: we earn a commission if you buy through our links, at no extra cost to you. It never changes which pan we recommend, and we’ll happily tell you to keep the skillet you already own. Full disclosure.

The short answer: the big number is a size, and it is not inches. A No. 8 skillet measures 10.625 inches across the top. A No. 10 measures 11.75. A No. 5 measures 8 inches — so the pan whose number happens to match its diameter is the No. 5, which is exactly the sort of coincidence that keeps the misunderstanding alive. If there is a second, usually smaller number, that is a pattern number identifying the mould, and any letter beside it distinguishes one mould of that pattern from another.

This matters for money. Buy a “No. 8” expecting an 8-inch pan and you will get something a touch larger than a classic 10.25-inch Lodge. Buy a “No. 10” and you are closer to a modern 12-inch, at nearly twelve inches of rim — a pan that will overhang most home burners.

The measured size chart

These figures come from the skillet and dutch oven size chart that the Wagner and Griswold Society links from its own educational resources page. They are measurements of real pans rather than a nominal standard, which is why they are not round numbers.

Skillets

  • No. 3 — 6.5 in top, 5.25 in bottom, 1.25 in deep
  • No. 4 — 7 in top, 5.75 in bottom, 1.5 in deep
  • No. 5 — 8 in top, 6.75 in bottom, 1.75 in deep
  • No. 6 — 9.125 in top, 7.5 in bottom, 1.875 in deep
  • No. 7 — 9.875 in top, 8.25 in bottom, 2 in deep
  • No. 8 — 10.625 in top, 8.875 in bottom, 2 in deep
  • No. 9 — 11.375 in top, 9.5 in bottom, 2 in deep
  • No. 10 — 11.75 in top, 10 in bottom, 2.125 in deep
  • No. 11 — 12.5 in top, 10.875 in bottom, 2.125 in deep
  • No. 12 — 13.375 in top, 11.75 in bottom, 2.25 in deep
  • No. 13 — 14.25 in top, 12.75 in bottom, 2.25 in deep
  • No. 14 — 15.25 in top, 13.5 in bottom, 2.25 in deep

Dutch ovens

  • No. 6 — 8.25 in top, 3.625 in deep, 2.5 qt
  • No. 7 — 9.25 in top, 3.75 in deep, 3.5 qt
  • No. 8 — 10.125 in top, 4 in deep, 4.5 qt
  • No. 9 — 11.25 in top, 4.25 in deep, 6 qt
  • No. 10 — 12.25 in top, 4.875 in deep, 8 qt
  • No. 11 — 13.25 in top, 6 in deep, 12 qt
  • No. 12 — 14.25 in top, 7 in deep, 15 qt
  • No. 13 — 15.25 in top, 8 in deep, 20.5 qt

Two things to notice. The skillet and pot tables do not agree at the same number— a No. 8 skillet is 10.625 inches and a No. 8 pot is 10.125 — so you cannot carry a number between categories. And capacity in the pot table climbs far faster than diameter, because the pots get deeper as well as wider: a No. 9 at 6 quarts becomes a No. 11 at 12 quarts over two inches of rim.

Where the numbers came from, and what we will not claim

The story you will read everywhere is that the numbers correspond to the diameter of the round openings — the “eyes” or holes — in the tops of wood and coal ranges, into which cookware was dropped so that it sat in direct contact with the fire. That is consistent with the bottom diameters in the chart above, and with the existence of heat rings, which raised a pan slightly on a stove of that era.

We are going to stop short of asserting it as fact, because we cannot cite it properly. The size chart the collectors’ society links is tables only — it publishes no explanation of what the numbers represent. The society’s own FAQ explains pattern numbers and defines heat rings but does not explain the origin of the size numbers. So: a widely repeated, entirely plausible account, which we have not been able to source to a publishing authority. If you want the definitive answer, the society’s educational page points at a reference-book list, and the collector literature is where it will be settled.

Pattern numbers and letters

The second number does a different job entirely. In the society’s own words: “Each piece of iron has to have its own mold… each pattern has a different letter… after the pattern number which would be the same number for like items.”

Unpacked: identical items share a pattern number, and individual moulds of that pattern are distinguished by a letter. That is why two apparently identical pans can show the same number with different letters, and why collectors care about letter variations that mean nothing at all to a cook. For Griswold specifically, the society’s dated chart notes that the third ERIE series, around 1892 to 1905, was the first with pattern numbers— which makes the presence or absence of a pattern number itself a dating clue on that brand.

The system is still alive

The surprising part is how much of this survives in pans sold new today. Field Company sells its skillets as numbers — the No. 8 is a 10.25-inch pan with a published 8.75-inch cooking surface. Lancaster sells a No. 10 that measures 11.6 inches across, which is within a sixth of an inch of the century-old chart figure of 11.75 for a No. 10. Those makers are deliberately picking up a convention their customers recognise.

Lodge went the other way and sells in inches — 3.5, 5, 6.5, 8, 10.25, 12, 13.25, 15 — which is why nobody has ever been confused by a Lodge box and everybody is confused by a flea-market pan. If you own both, it is worth internalising one conversion: a vintage No. 8 sits between a modern 10.25 and a modern 12.

Pans that live on both sides of the system

Ranked on published specs, build and buyer fit. Select a row to jump to the full write-up. We haven’t cooked in all of these — here is exactly what we do instead.

#ProductBest forPrice
1
Lodge Classic 10.25-inch Skillet

Lodge Classic 10.25-inch Skillet

The pan most people should buy and stop thinking about. Pre-seasoned, made in the USA, oven-safe to anything, and about $25 — the value is so lopsided that the expensive pans have to justify themselves against it, not the other way around.

Best pan sold in inches
$24.90 · View on Amazon

Price as of October 11, 2026. #ad How we’re funded

2
Field Company No. 8 Cast Iron Skillet (10.25-inch) with Cleaning Kit

Field Company No. 8 Cast Iron Skillet (10.25-inch) with Cleaning Kit

The heirloom pick that's actually usable every day: a machined-smooth cooking surface and a lighter body than the Lodge, made in the USA. Amazon no longer lists this pan on its own — what you buy is the same No. 8 packed with Field's cleaning kit, at roughly eight times a classic Lodge, so it earns the money only if the polish and the lighter weight are things that specifically bother you.

A No. 8 you can buy new
$200.00 · View on Amazon

Price as of October 11, 2026. #ad How we’re funded

3
Lancaster No. 10 Cast Iron Skillet (11.6-inch)

Lancaster No. 10 Cast Iron Skillet (11.6-inch)

A big, machined-smooth American pan with an unusually large 10-inch cooking surface for its class — more usable flat space than most 12-inch skillets. A specialist heirloom buy, not a first pan.

A No. 10 you can buy new
$225.00 · View on Amazon

Price as of October 11, 2026. #ad How we’re funded

The picks in full

#1Best pan sold in inches

Lodge Classic 10.25-inch Skillet

The pan most people should buy and stop thinking about. Pre-seasoned, made in the USA, oven-safe to anything, and about $25 — the value is so lopsided that the expensive pans have to justify themselves against it, not the other way around.

Strengths

  • Around $25 for a lifetime pan — nothing else here is close on value
  • Made in the USA and sold pre-seasoned, so it cooks the day it arrives
  • Thick walls hold heat well for searing

Trade-offs

  • Slightly pebbled cooking surface (it smooths with years of use)
  • Short handle gets hot and gives little leverage for 5+ lb of iron
  • Heavier than the machined 'heirloom' pans
MaterialBare cast iron
Diameter10.25 in
Weight5.36 lb
Oven-safe toAny oven temp
Induction-readyYes
Made inUSA
WarrantyLifetime (Made Right)

Spec note. Lodge's published weight is 5.36 lb for the 10.25-inch. It ships pre-seasoned from the foundry, so it's usable immediately — you just keep the seasoning up. Bare iron has no upper oven-temperature limit.

Specs read from the manufacturer and product listing, on July 20, 2026. “Not published” means the maker doesn’t state that figure.

#2A No. 8 you can buy new

Field Company No. 8 Cast Iron Skillet (10.25-inch) with Cleaning Kit

The heirloom pick that's actually usable every day: a machined-smooth cooking surface and a lighter body than the Lodge, made in the USA. Amazon no longer lists this pan on its own — what you buy is the same No. 8 packed with Field's cleaning kit, at roughly eight times a classic Lodge, so it earns the money only if the polish and the lighter weight are things that specifically bother you.

Strengths

  • Machined-smooth surface is slicker than raw Lodge from day one
  • Lighter (about 4.5 lb) than a classic Lodge of the same size
  • Made in the USA, backed for life, and the care kit is already in the box

Trade-offs

  • Around eight times the price of a Lodge that cooks the same food
  • Thinner, so a touch less heat retention than a heavy Lodge
  • Amazon has no bare-pan listing left, so the set is the only way in
MaterialBare cast iron
Diameter10.25 in
Cooking surface8.75 in
Weight4.5 lb
Oven-safe toAny oven temp
Induction-readyYes
Made inUSA
WarrantyLifetime

Spec note. Field lists 4.5 lb on its spec table (4.3 lb in the description). The cooking surface is about 8.75 in across on a 10.25-in pan. We point at the starter-set listing rather than the bare pan because on 2026-09-29 a live Creators API call returned no item at all for the bare No. 8's former ASIN, and no standalone No. 8 exists on Amazon any more — the pan is sold there only in sets. This listing publishes a 10.25-inch pre-seasoned skillet made in the USA plus Field's cleaning kit: a natural-fibre brush, a chain-mail scrubber and a bottle of organic seasoning oil. The other live sets carrying the same pan add a matching No. 8 lid and cost more. Bare iron has no upper oven-temperature limit.

Specs read from the manufacturer and product listing, on September 29, 2026. “Not published” means the maker doesn’t state that figure.

#3A No. 10 you can buy new

Lancaster No. 10 Cast Iron Skillet (11.6-inch)

A big, machined-smooth American pan with an unusually large 10-inch cooking surface for its class — more usable flat space than most 12-inch skillets. A specialist heirloom buy, not a first pan.

Strengths

  • Genuinely large 10-in flat cooking surface
  • Machined-smooth, lighter than a Lodge of similar footprint
  • Made in the USA, heirloom build

Trade-offs

  • Premium price — many times a Lodge
  • Warranty terms aren't clearly published on the product page
  • Big and still six pounds — not a nimble everyday pan
MaterialBare cast iron
Diameter11.6 in
Cooking surface10 in
Weight6 lb
Oven-safe toAny oven temp
Induction-readyYes
Made inUSA
WarrantyNot published

Spec note. Weight 6 lb; the flat cooking surface is about 10 in across, unusually large for an 11.6-in pan. Warranty terms weren't published on the product page at the time of writing.

Specs read from the manufacturer and product listing, on July 20, 2026. “Not published” means the maker doesn’t state that figure.

How to use the chart when you are standing in a shop

Carry a tape measure. Measure across the top of the pan, outside rim to outside rim, and check it against the table. If the number on the bottom and your measurement agree, the pan was built to the old American standard and the number is a size. If they do not agree, the number is probably a pattern number and the size is not marked at all.

Then measure the bottom, because that is the figure that decides whether the pan will work on your stove. The chart gives a No. 8 an 8.875-inch bottom and a No. 10 a 10-inch bottom, and those are the dimensions that have to relate to your burner. On a radiant glass cooktop, GE publishes a rule that pans should not overhang a burner by more than one inch per side; on induction, GE and Whirlpool both want the base matched to the cooking circle or the burner may not detect the pan at all. We go through both in best cast iron for a glass top stove and best cast iron for an induction cooktop.

One last practical note. If all you want is to know which size pan to buy, skip the whole system: modern makers that sell in inches have removed the ambiguity on purpose, and our size guide maps each one to what it is good for. The numbers matter when you are buying old iron, selling old iron, or trying to work out why the “8-inch” pan you bought online turned out to be bigger than your biggest burner.

Frequently asked questions

What do the numbers on cast iron skillets mean?

The large number is a size in a legacy system that is not inches. The measured chart the collectors' society links gives No. 3 as 6.5 inches across the top, No. 5 as 8 inches, No. 6 as 9.125, No. 8 as 10.625, No. 10 as 11.75 and No. 12 as 13.375. A second, often smaller number is usually a pattern number identifying the mould the pan was cast from, sometimes with a letter beside it.

Is a No. 8 skillet 8 inches?

No — it is 10.625 inches across the top, over an 8.875-inch bottom, about 2 inches deep. That is the single most useful fact on this page, because it means a vintage No. 8 is a slightly larger pan than a modern classic 10.25-inch skillet, and a vintage No. 10 at 11.75 inches is closer to a modern 12-inch than to a 10.

Where do the cast iron numbers come from?

They are an industry-standard sizing system inherited from the era of wood and coal ranges, where cookware had to drop into the round openings in a stove top. We will not state more than that with confidence: the size chart the collectors' society links publishes measurements only and no explanation, and the society's own FAQ explains pattern numbers without explaining the origin of the size numbers. The widely repeated stove-eye story is plausible and, in the sources we can cite, unverified.

What is a pattern number on cast iron?

An identifier for the mould rather than the pan's size. The Wagner and Griswold Society explains it this way: "Each piece of iron has to have its own mold… each pattern has a different letter… after the pattern number which would be the same number for like items." So like items share a number and individual moulds are distinguished by a letter — which is why two identical-looking pans can carry the same number with different letters.

Do modern cast iron pans use the old numbers?

Some do, and the continuity is remarkable. Field Company sells a No. 8 and Lancaster a No. 10; Lancaster's No. 10 measures 11.6 inches, within a sixth of an inch of the century-old chart figure of 11.75 for a No. 10. Lodge, by contrast, abandoned the system entirely and sells in inches — 8, 10.25, 12, 15 — which is why a Lodge box never confuses anybody and a flea-market pan always does.

What does a letter next to the number mean?

It identifies which mould of a given pattern the piece came from. Per the society, each pattern has a different letter after the pattern number, with the number shared across like items. Letters are a production detail rather than a quality marking, and they are useful mainly to collectors matching variations.

Do dutch oven numbers work the same way?

Same system, different table. The chart gives No. 6 as 8.25 inches across the top at 2.5 quarts, No. 8 as 10.125 inches at 4.5 quarts, No. 9 as 11.25 inches at 6 quarts, No. 10 as 12.25 inches at 8 quarts and No. 12 as 14.25 inches at 15 quarts. Note that the pot and skillet tables do not agree at the same number — a No. 8 skillet is 10.625 inches and a No. 8 pot is 10.125.

Why does my pan have a number but no maker's name?

Because many American foundries used the same numbering system and not all of them marked their work, and because some pans were cast from moulds whose markings had been obscured. A lone number is still useful: measure the rim and check it against the chart, and if the two agree you are holding a pan built to the old American standard.

Does the number tell you how old a pan is?

Not on its own. The size number says what size it is in the old system, which tells you it is old American-standard iron but not which decade. Dating comes from the maker's mark, the gate mark, the heat ring, wall thickness and surface finish — and for Griswold specifically from the collectors' society's dated trademark chart.

Sources

  • panman.com — Cast Iron Skillet and Dutch Oven Size Charts — The size chart the Wagner and Griswold Society links from its own educational page, giving measured top diameter, bottom diameter and depth per number. Skillets: No. 3 = 6.5 in top / 5.25 in bottom / 1.25 in deep; No. 4 = 7 / 5.75 / 1.5; No. 5 = 8 / 6.75 / 1.75; No. 6 = 9.125 / 7.5 / 1.875; No. 7 = 9.875 / 8.25 / 2; No. 8 = 10.625 / 8.875 / 2; No. 9 = 11.375 / 9.5 / 2; No. 10 = 11.75 / 10 / 2.125; No. 11 = 12.5 / 10.875 / 2.125; No. 12 = 13.375 / 11.75 / 2.25; No. 13 = 14.25 / 12.75 / 2.25; No. 14 = 15.25 / 13.5 / 2.25. Dutch ovens: No. 6 = 8.25 in top / 2.5 qt; No. 7 = 9.25 / 3.5 qt; No. 8 = 10.125 / 4.5 qt; No. 9 = 11.25 / 6 qt; No. 10 = 12.25 / 8 qt; No. 11 = 13.25 / 12 qt; No. 12 = 14.25 / 15 qt; No. 13 = 15.25 / 20.5 qt. The chart is tables only — it publishes no explanation of what the numbers represent (accessed October 11, 2026)
  • Griswold and Cast Iron Information Board (Wagner and Griswold Society) — FAQ — The society's own FAQ, which is the only place it publishes Wagner dates in prose: "Randall Corp. bought Wagner in Nov. 1952"; "McGraw Edison Inc. bought Griswold on March 29, 1957" and "then sold it in December 1957 to Randall who already owned Wagner", after which "all subsequent 'Griswold' pieces were made in the Wagner foundry in Sidney, Ohio" and do not say Erie on the piece; "During the later 1970's and/or early 1980's many pieces were marked with BOTH the Wagner and Griswold trademarks (logos) on the bottom"; "In 1991 a new line of Wagner pieces marked 'Wagner's 1891 Original' was put into production to celebrate Wagner's 100th anniversary. This is the line that remained in production as a regular production item until the foundry closed in 1999"; on numbers, "Each piece of iron has to have its own mold… each pattern has a different letter… after the pattern number which would be the same number for like items"; and on heat rings, "The heat ring is the small rim around the outside of the bottom of many (usually earlier) skillets". It also records the collector view that "Most collectors do not consider Griswold pieces made in Sidney to be real Griswold" and that "almost any pieces made after 1960 has limited collector appeal" (accessed October 11, 2026)
  • Wagner and Griswold Society — Educational Resources — The society's own index of identification references, which is what it points collectors at rather than publishing a single key: the FAQ, a Griswold trademark page, a reproductions and fakes page, a references and books list, and an external skillet and dutch oven size chart (accessed October 11, 2026)
  • Wagner and Griswold Society — Griswold Skillet Chart (R. G. Meadows, 2017) — The collectors' society's own dating chart for Griswold skillets, crediting Steve Stephens as the primary source for the dates: ERIE first series c1880-c1886, second series c1886-c1892, third series (the first with pattern numbers) c1892-c1905, GRISWOLD'S ERIE c1905-c1907, slant trademark with ERIE c1907-c1909, slant trademark with ERIE PA USA c1909-c1924 (heat ring first, smooth bottom from about 1916), block trademark c1916-c1940, small trademark from the late 1930s to c1952, the late large trademark c1952-1957, and the VICTOR budget line in the 1940s and 1950s (accessed August 18, 2026)
  • Lancaster Cast Iron — First Time Use & Care Guide — Lancaster's own break-in advice: use extra oil for the first dozen cooks, avoid acidic ingredients until the seasoning is developed, dry on low heat and oil while warm (accessed August 11, 2026)
  • Field Company — Cast Iron Care & Maintenance Guide — Field's care routine and design rationale for a lighter, machined-smooth pan (accessed July 20, 2026)
  • Lodge Cast Iron — Cast Iron Product Guide — Lodge's own guide to which piece does which job — skillets, griddles, grill pans, woks and bakeware (accessed August 11, 2026)

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