ATX vs Micro-ATX Motherboards
ATX is the full-size standard at 305 × 244 mm with up to seven expansion slots. Micro-ATX shortens it to a 244 mm square with up to four. With the same processor and graphics card the two perform identically, so the real question is what you give up: expansion slots, memory slots and, on the cheaper Micro-ATX boards, how much power the board is wired to feed a processor.
The verdict
For a single graphics card and no add-in cards, Micro-ATX gives up very little and often costs less. Step up to ATX when you want four memory slots as a certainty, more M.2 storage, or the stronger power delivery that the larger boards tend to carry.
The physical difference
These are fixed standards, the same for every board of that size.
Cases, cooling and what fits
Most of what people worry about here is decided by the case, not the board.
Which case takes which board
A case is built around one board size and accepts that size plus anything smaller, never anything larger. So a case rated for the larger of these two will happily take the smaller one, using a different set of standoffs, while the reverse does not physically fit. Picking the smaller board does not commit you to the smaller case.
Cooler height and graphics card length
Both limits are published by the case, not the board, and they are the two numbers most likely to catch you out in a small build. Check the maximum CPU cooler height and maximum graphics card length on the case you have in mind before you order either part.
What you give up, in numbers
How the two sizes actually differ once you look at every board on sale, rather than at what the standard permits. Measured across 217 ATX and 149 Micro-ATX boards at the retailers we track (201 and 136 in stock today), and updated daily.
The picks on each side
The cheapest board on each side, and the cheapest one that clears a floor worth clearing: enough power headroom for the socket’s top processor, and Wi-Fi 6E or better. Recalculated daily from live prices.
ATX
Best all-round
$118.99 · cheapest with the power headroom and Wi-Fi worth having
Micro-ATX
Best all-round
$99.99 · cheapest with the power headroom and Wi-Fi worth having
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Common questions
Is there a downside to Micro-ATX?
Three, and they are all worth checking on the specific board rather than assuming: fewer expansion slots, a real chance of only two memory slots instead of four, and weaker power delivery on the budget models. For a single-graphics-card build none of these usually limits you.
Can I use a Micro-ATX board in an ATX case?
Yes. ATX cases include the Micro-ATX mounting points, so a smaller board fits without adapters. You will have some empty space above the board and any unused case expansion slots stay covered.
How do I know if my motherboard is ATX or Micro-ATX?
Measure it, or count the rear expansion slots. ATX is 305 mm tall with up to seven slot positions; Micro-ATX is a 244 mm square with at most four.
Is ATX outdated?
No. ATX has been the desktop standard since 1995 and remains the most common size for new boards, because the extra area is what allows more expansion slots, more M.2 storage and heavier power delivery.
Keep going
Browse every ATX board or Micro-ATX board with filters, put two specific boards head to head, or read up on choosing a case to fit the board you pick.