Ita Bag Sizes Explained: A3, A4, Mini & 15.6 Inch
YueQuick answer: choose by pin count first, laptop second. Mini (under 18cm) suits 6-8 pins and daily carry; A4-style windows hold 20-30; A3 windows hold 50+; a 15.6-inch ita bag is a laptop bag with a display window - buy it when you actually carry a laptop, not for the pins.
There are five sizes that cover the whole ita bag market, and listings mix them freely - "A4 ita bag", "large ita bag", "mini ita bag" and "15.6 inch ita bag" each imply different window dimensions. This table maps the sizes to what you actually get.
Size comparison table
| Size | Window | Pins | Best for |
|---|---|---|---|
| Mini / A7 | ~14-16cm | 4-6 | Daily, first display, gifts |
| A6 / Small | ~16-18cm | 6-10 | Everyday bag, starter layout |
| A4 / Medium | ~21cm | 15-25 | Regular collectors, conventions |
| A3 / Large | ~30cm | 40-60 | Full collection transport |
| 15.6 inch laptop | varies | as room allows | Students & commuters |
The laptop trap
A "15.6 inch ita bag" optimises for the laptop first: padded sleeve, structured back, window as secondary feature. If you only want pins, a same-price A4 window bag will hold three times more display. Buy the laptop model for the laptop.
Insert sizing rule
Cut your insert 5mm smaller than the window on every side. For A4 windows that means roughly 200 x 290mm insert stock - and always trace your actual bag, since A4 body ≠ A4 window.
Measuring your window before you buy an insert
Two measurements decide everything: window width (left to right at the widest point) and window depth (front of the window to the insert backstop). Most shaped bags lie about their capacity - a heart window at 24cm wide has an effective circle of about 17cm. Take both numbers to the store page and ignore the marketing size on the listing.
Cut-list rule for each size: insert = window width minus 5mm per side, depth minus 10mm. A tracing pattern from an old insert (or a cut-out from paper) beats measuring a curved window with a ruler every time. Full cut walkthrough: DIY insert guide.
Pin capacity by size (the honest numbers)
| Size | Window | Medium pins (58mm) | Weight when full |
|---|---|---|---|
| Mini | 14-16cm | 4-6 | ~150g |
| Small / A6 | 16-18cm | 6-10 | ~250g |
| A4 / Medium | 21cm | 15-25 | ~450g |
| A3 / Large | 30cm | 40-60 | ~900g |
Weight matters more than people expect: at 450g+ the strap and shoulder stitching are doing real work, so check that the bag has reinforced strap anchors (bar-tack stitching, not single-row seams). Our large format bags list tested capacities.
Size for school, work and travel
- School backpacks must swallow a laptop sleeve AND a display - check both dimensions against your own bag before ordering
- 15.6 inch bags optimize for the laptop; expect a secondary window (20% of display capacity)
- Travel: A3 or A4 with rigid backing; soft minis crease under luggage straps
Sizing mistakes new collectors make
- Buying big for future pins - an oversized window with 5 pins reads incomplete; sizes grow with collections
- Confusing bag size with window size - a "large tote" can carry a small window; check both spec lines
- Ignoring insert depth - pins need 6-8mm of insert thickness to sit upright through a window sheet
Frequently asked questions
What size fits a convention beginner?
A4 / medium - 15-25 pins is the number most first-timers own after one year of collecting.
Do inserts come pre-cut?
Most ship rectangular and get trimmed to your window; shaped windows need a two-piece cut, see the measuring chart above.
Can I upgrade the strap instead of the bag?
Yes - a wider strap buys about 100g of comfort before the limit. Chains and straps live in ita bag chains.
The full size chart (what sellers won't tell you)
| Label | Real bag size | Window size | Fits laptop | Pins (medium) |
|---|---|---|---|---|
| Mini | 18x14x6cm | 12x9cm | No | 4-6 |
| Small | 24x18x7cm | 16x12cm | No | 6-10 |
| Medium / A4 | 32x24x10cm | 21x15cm | Tablet only | 15-25 |
| Large / A3 | 40x30x12cm | 30x21cm | 13-15" tight | 40-60 |
| Backpack | 44x32x14cm | secondary 20x15cm | 15.6" | 12-18 in window |
Two numbers explain most buyer's remorse: window size (display capacity) and depth (what else fits behind it). Bags listed only by "dimensions" usually quote the outer shell - always find the window spec or ask. Matching inserts: ita bag inserts.
Matching size to collection growth rate
- Casual buyer (2-4 pins a year): small, forever - small windows look intentional with few pins
- Convention collector (one haul a year): medium; it holds a typical year-one collection at 65% fill
- Trader / active seller: large or A3 - stock visibility is inventory
- Gift buyer unsure of habits: medium, plus a gift receipt - the format with the widest error margin
Growth math beats current-collection math: buy for the collection you'll have in 18 months, not the one you have today, but never two sizes up - an oversized window with sparse pins reads unfinished (more on that in the one-badge guide).
Depth, inserts and the hidden 8mm rule
Pins need 6-8mm of insert thickness to stand upright through a window sheet - thinner foam lets badges tilt forward and touch the vinyl, which fogs and scratches over time. Firm (28-32 kg/m³) foam holds pin shafts best; craft-store 20 kg/m³ foam collapses within months. Measure your bag's interior depth before choosing: total = insert thickness (8mm) + pin length (6-10mm) + clearance (5mm) = ~20-23mm minimum behind the window. Cutting methods: DIY insert guide.
International sizing conventions to ignore
Japanese bags run one size smaller than Western equivalents ("M" in Japan ≈ "S" elsewhere). A6/A4/A3 labels refer to paper sizes and are reliable; vague labels like "large-capacity" are not. When ordering cross-border, trust the cm table above over any size letter.
Frequently asked questions
What size do most conventions ask for?
Nothing - but many venues limit bag dimensions at security (usually 30x30x15cm); medium bags pass everywhere.
Is bigger always better for photos?
No: at thumbnail size, a full A3 wall becomes texture. Focal displays perform; texture recedes.
Can a medium bag carry a full day's stuff?
Phone, wallet, keys, snack - yes if the insert stays the priority. Camera gear, no; that's backpack territory (backpacks).
How do I know my insert is the right thickness?
Pin it and tilt the bag 45° forward - if badges stay parallel to the window, the foam is right.
Shop the theme
FAQ
What size ita bag should a beginner buy?
A6/small - enough for 6-10 pins, still light enough for daily use. Upgrading is cheap; an oversized bag with empty window reads as a mistake.
What is the biggest size?
A3 display windows, typically built as backpacks or large totes - useful for travel, heavy for daily carry.
