Why is Gridfinity 42 mm? What Zack Freedman said, and what the number does for your drawer
28 September 2026
Gridfinity is 42 mm because 42 divides into a lot of other numbers. Zack Freedman, who created the system, said it himself in the Gridfinity 2.0 video: he picked 42 "because it divides evenly into many other numbers, which makes it more likely your stuff will nest into your storage and more likely your storage will nest into your drawers. It's also a bit of a literary reference."
So the famous answer, the Hitchhiker's Guide one, is true, but by his own account it is the smallest of the reasons.
Everything he has said about it
I went looking for every place he explains the number, because the question comes up under nearly every Gridfinity post and most answers online are guesses.
- In the 2023 video quoted above: easy to divide, more likely to nest, plus the literary reference. The same video then announces that Gridfinity 2.0 is 50 mm wide and 15 mm tall. That part is an April Fools joke. The grid is still 42.
- In a tweet from March 2023: "Lots of factors to make mental math easy, and higher chance of baseplates nesting neatly into drawers."
- In a reply under the original 2022 video, to someone asking how he settled on 42: "Partially because it's easy to divide with mental math, partially because that lets you use microscope slides as windows in the glass-front bins." The window bin is in that video at about 11 minutes, one wall replaced by a slide.
The original video states the rules and nothing more. Every bin fits inside whole 42 mm squares, and every bin is a multiple of 7 mm tall. It never says why.
What people add, and whether it holds
42 is 6 times 7, and the height unit is 7 mm. Fans read that as the reason for both numbers. It fits, but Zack has never explained the 7.
A reply quoted on Reddit has him saying the next round option was 60 mm, and that owners of Prusa-sized printers could then print baseplates of only 3 by 3. I could not find the original post, so treat that one as unconfirmed. The arithmetic behind it holds up. The short side of a 250 by 210 bed takes three 60 mm cells and no more.
What 42 means on your printer
This is the part that decides your plates. A baseplate is a whole number of cells, so the question is how many 42 mm cells fit on the bed:
- 180 mm bed (Prusa Mini, Bambu A1 mini): 4 cells, 168 mm.
- 220 or 235 mm bed (Ender 3 and relatives): 5 cells, 210 mm.
- 250 by 210 mm bed (Prusa MK3 and MK4): 5 by 5 cells, 210 mm square.
- 256 mm bed (Bambu X1, P1, A1): 6 cells, 252 mm.
- 350 mm bed (Voron 350, Ender 5 Plus): 8 cells, 336 mm.
The 250 mm bed is the trap. Six cells are 252 mm, 2 mm too long for it. My own drawer planner cut every baseplate into 6 cell pieces until last week, because I had sized it for my Bambu. Anyone planning a drawer on a Prusa got pieces their printer could not take. The planner now asks for the bed size first and cuts the plate to fit it, with solid edges that fill the rest of the drawer.
The rest of the standard hangs off the same two numbers. A bin is 41.5 mm per cell on the outside, 0.25 mm of clearance on each side. The foot is 4.75 mm tall, the magnets are 6 by 2 mm in 6.5 mm pockets, and the screws are M3. I wrote all of it down in Gridfinity dimensions explained. The Gridfinity generator builds any bin or plate on that grid, and its drawer planner does the cutting for your bed.
Half cells and inches
There is no official half grid. The community made one anyway, with 21 mm half cells and their own baseplates. They do not sit in a standard 42 mm plate, which is why I left them out of my generator for now. There is no official inch version either. Gridfinity is metric, and 42 mm is 1.65 inches, which divides into nothing.