What does 100+ actually mean on a deck box?

"100+" is a manufacturer's stated capacity, not a promise about your specific deck. Most boxes carrying that label list separate numbers for unsleeved cards, single sleeved cards, and double sleeved cards, and the double sleeved figure assumes one particular sleeve combo, often the brand's own. The Ultimate Guard Boulder 100+ is the textbook example: it's rated for 100 double sleeved, 120 single sleeved, and 210 unsleeved cards, and its interior measures 68.3mm, one of the smallest interiors of any 100+ box we've checked. Run Dragon Shield Mattes through it and reviewers and forum users report it flatly does not close. Run KMC Hyper Mats through the same box and it closes with a couple millimeters to spare. Same sticker, two different real answers depending on what's actually in your hand.

The plus sign means "our test case," not "your case"

When a brand prints three capacity numbers on one box, it's telling you the box was measured against three assumptions: bare cards, one sleeve layer, and two sleeve layers. That's useful information, but it collapses the moment you plug in a sleeve brand that runs thicker or thinner than whatever the manufacturer used internally. Dragon Shield Mattes are a known thick outer sleeve. KMC and Gamegenic combos tend to run thinner. A box built and rated around one of those assumptions can pass with the other and fail with the first, and the label never distinguishes between them.

This is also why two boxes can share an identical "100+" rating and behave nothing alike. The rating describes what the manufacturer verified, not what every sleeve combo on the market will do inside that specific interior.

Real examples where the label and the tape measure disagree

Look at the Vault X row closely. Vault X officially rates that box at 100 double-sleeved cards, and that's true for the thinner combos on the market. But independent measurement puts its interior at 67.3mm, which is short of what a Dragon Shield Matte based stack needs. Both things are true at once: the manufacturer number and the community measurement, describing different sleeve assumptions. That's the whole "100+" problem in one box.

The Ultra Pro Eclipse 2-Piece is the cleanest counter-example. It only carries a single-sleeved rating, and at 66.4mm interior, that's honest. Nobody promised it would hold a double sleeved deck, and it doesn't.

Why the same number hides different interiors

Two boxes both marked "100+" can differ by more than 20mm in interior depth once you compare the Boulder 100+ at 68.3mm against the Dragon Shield Double Shell's 90mm. The label tells you a headline capacity. It never tells you the margin, and margin is exactly what determines whether your specific sleeves close the lid. A box with barely enough room for its own tested combo has zero margin for anything thicker, while a box built with real headroom shrugs off almost any sleeve you throw at it.

If you own multiple Boulder sizes already and want to stick with the line, the whole family's real capacities are broken down in our Ultimate Guard Boulder size guide, including where each size actually earns its rating and where it's optimistic.

Quick answers

Does "100+" ever mean the box holds more than 100 cards? Sometimes, yes, especially unsleeved. The "+" is really flagging "at least this many under favorable conditions," and favorable conditions vary a lot between double sleeved Commander cards and a stack of bare bulk commons.

Why do some 100+ boxes only list a single sleeved number? Because the manufacturer didn't test or doesn't recommend double sleeved use in that box. Treat the absence of a double sleeved number as a real signal, not an oversight.

Is a bigger stated number always the safer buy? No. A box rated "133+" with an unknown interior tells you less than a box rated "100+" with a confirmed 78mm interior. Depth and verified fit beat the number printed on the front every time.

Check your exact sleeve combo against a box's real interior with the fit checker before you order anything, and see the full list of boxes confirmed to fit 100 double sleeved cards if you'd rather skip the guesswork entirely. The sticker on the box was never lying, exactly. It just wasn't answering the question you were asking.