1911 Magazines and Capacity: How Many Rounds, Extended Mags and Single vs Double Stack

There is a lot of confusion about 1911 magazines, so Bob Serva from Fusion Firearms breaks it down. The most common mistake is thinking the magazine body itself is a different width depending on caliber. It is not. On a standard single-stack 1911, the opening in the frame is the same for a .45 ACP, a 9mm, a 10mm, a .40 S&W, or a .38 Super. The magazine that drops into that frame is the same body width for all of them. What actually changes is capacity, the internal feed geometry, and the magazine length that matches your frame size. This guide walks through how many rounds a 1911 holds, the difference between single-stack and double-stack, extended magazines, 9mm versus .45 magazines, and how to pick the right one.

How many rounds does a 1911 hold?

Capacity comes down to two things: the caliber and the frame size. A full-size single-stack 1911 in .45 ACP holds 7 rounds in a standard magazine, and 8 rounds in an extended-capacity full-size magazine. Step down to a smaller round and the same size magazine holds more, because the cartridges are narrower. A full-size 1911 in 9mm holds 9 or 10 rounds. A .38 Super full-size holds 9 rounds, and a 10mm or .40 S&W full-size holds 8 rounds.

Frame size sets the magazine length, which caps how many rounds fit. A government or commander frame uses a full-size magazine. An officer or defender frame has a shorter grip, so it takes a shorter magazine that holds a round or two fewer. A 9mm officer magazine holds 7 to 8 rounds, and a .45 ACP officer magazine holds 6.

These are the real capacities from the 1911 magazines Fusion stocks, not rounded estimates.

Capacities based on the 1911 magazine lineup Fusion Firearms stocks. On a phone, swipe the table sideways to see every column.

Single stack vs double stack capacity

The single-stack 1911 is the original John Browning design. Cartridges sit in a single column, which keeps the grip slim and the gun classic. That slim grip is part of why people love the 1911, and it is also why a single-stack tops out around 7 to 10 rounds depending on caliber.

A double-stack 1911, often called a 2011, stages cartridges in a staggered two-column column inside a wider grip. That is how you get well past single-stack capacity in the same overall pistol length. The Fusion XP Pro is a double-stack 9mm built on this pattern. It runs Glock 17 magazines and holds 17 rounds, so you carry ten more rounds than a single-stack 9mm without changing how the gun shoots. Where high-capacity magazines are restricted, the XP Pro also runs a 10-round magazine. If you want the full breakdown of the platform, read our double-stack 1911 guide on the XP Pro.

What are extended magazines?

There are two different things people mean by "extended" magazine, and it helps to keep them straight.

• Extended-capacity full-size magazine. A magazine built to add a round over the standard count, like an 8-round .45 ACP full-size instead of 7. It still fits flush in the frame.
• Magazine extension. A part that bolts onto the base of a magazine to add capacity. On Fusion's double-stack platform, the Glock +5 magazine extension adds 5 rounds to a Glock 17 magazine, taking the XP Pro from 17 to 22 rounds.
• Full-size magazine in a smaller frame. You can run a full-size magazine in an officer or defender frame. It fits the same mag well, but it sticks out past the bottom of the short grip, so it does not sit flush.

If you want the XP Pro at 22 rounds, the magazine extension is the move. We cover the install step by step in our Glock +5 magazine extension installation guide, so we will not repeat all of it here.

1911 9mm vs .45 magazines: what is the same and what is different

The outside body of a single-stack 1911 magazine is the same width and profile regardless of caliber. A 9mm, a .45 ACP, a .38 Super, a 10mm, and a .40 S&W magazine all drop into the same mag well opening on a government or commander frame. So the frame opening is not bigger for a .45 than it is for a 9mm. They are all the same size.

The differences live inside the magazine. The feed lips and the follower are tuned to the cartridge so the rounds stack and feed correctly. The .45 ACP pretty much stands on its own here. A .45 ACP magazine is built for the .45 ACP group. The 9mm, .40 S&W, and 10mm share more in common with each other in feed-lip and follower design. The practical takeaway: buy the magazine that matches your caliber and your frame size, and buy quality. Cheap magazines with weak feed lips or a sticky follower are the most common cause of feeding problems in an otherwise good 1911. If you want a primer on how a magazine actually works, see what is a gun magazine. For the caliber decision itself, our 9mm vs .45 ACP comparison goes deeper.

Choosing a 1911 magazine

Pick a magazine with three things in mind, in this order:

• Frame size first. Government and commander frames take full-size magazines. Officer and defender frames take the shorter officer-length magazines. A full-size magazine will fit a short frame, but it hangs below the grip.
• Caliber second. Match the magazine to your chambering so the feed lips and follower are right for the round.
• Capacity needs third. Standard for everyday carry and flush fit, extended-capacity or a magazine extension when you want more rounds, or a compliant 10-round option where local law requires it.

Browse the full 1911 magazine selection by caliber and frame, the Glock magazine extensions for the XP Pro, or grab a 1911 parts kit while you are building out your pistol.

Frequently asked questions about 1911 magazines and capacity