ATX is the standard full-size desktop motherboard: 305 × 244 mm, up to seven expansion slot positions and normally four memory slots. It fits any mid-tower or full-tower case, and it is the size with the widest choice of models at every price. If you have no particular reason to build small, ATX is the default, and the boards we track are on the ATX motherboard deals page.
Cheapest ATX boards right now
All 409 ATX motherboards, with price drops and price history
Amazon Warehouse offers on ATX boards
What ATX is
ATX is a specification first published by Intel in 1995. It fixes the outline of the board, the positions of the mounting holes, the location of the rear port panel and the placement of the expansion slots, so that any ATX board fits any ATX case. Micro-ATX and Mini-ITX are smaller sizes that reuse a subset of the same mounting holes and the same rear panel position, which is why a small board fits a large case.
| Form factor | Maximum size | Expansion slot positions | Typical memory slots |
|---|---|---|---|
| E-ATX | Loosely defined; wider than ATX | Seven | Four, or eight on workstation boards |
| ATX | 305 × 244 mm | Seven | Four |
| Micro-ATX | 244 × 244 mm | Four | Four, or two on budget boards |
| Mini-ITX | 170 × 170 mm | One | Two |
Expansion slots and memory slots
The specification allows seven expansion slot positions, but few modern ATX boards fit a PCIe slot in every one. Board makers now use much of that space for M.2 drives and their heatsinks, and they leave gaps below the main graphics slot because a current graphics card covers two or three positions anyway. A typical ATX board has one full-length slot for the graphics card, one or two more full-length slots wired for fewer lanes, and perhaps a short slot or two. How many slots there are, and how each is wired, varies by board, so read the specification if you plan to fit a capture card, a network card or a second graphics card.
Nearly all ATX boards have four memory slots, two for each of the processor's two memory channels. That lets you start with two modules and add two later, although two modules are generally easier to run at high speed than four.
What the larger board most reliably buys you is room: more M.2 slots, more fan and pump headers, more SATA ports, more USB headers for the case's front panel, and more space around the processor socket for a large cooler.
Case compatibility
An ATX board needs a case that lists ATX support, which means a mid-tower or a full-tower. It will not go into a Micro-ATX or Mini-ITX case. The rule only works one way: a smaller board fits a larger case, not the reverse.
One detail is worth knowing on cheaper models. Some boards sold as ATX are the full 305 mm tall but narrower than 244 mm. They fit any ATX case, but they do not reach the right-hand column of standoffs, so the edge with the main power connector is unsupported. Support that edge with your fingers when you push the 24-pin cable in.
Cooling and cable routing
ATX is the easiest size to build in and to keep cool. Components are spread out, so M.2 drives are less likely to sit directly under a hot graphics card, the power delivery heatsinks can be larger, and tall air coolers rarely foul the memory or the top slot. The power and data connectors sit along the top and right-hand edges, where a standard case has cut-outs for cables to pass behind the board tray. That makes a tidy build simple, which in turn helps airflow.
The trade-off is the size of the finished PC. A mid-tower takes up real space on or under a desk, and if you will only ever fit one graphics card and two drives, much of an ATX board's extra area goes unused.
Price tendencies
ATX has the broadest price range of any size. At the low end, the cheapest ATX board on a given chipset usually costs a little more than the cheapest Micro-ATX one, because entry-level models are made in the smaller size first. In the middle of the market the two sizes are often close. At the top, nearly all high-end boards are ATX or larger, so that is where the expensive models sit. Because so many ATX models are on sale, this is also where most price drops and open-box offers appear. How much to spend on a motherboard sets out where extra money stops buying anything useful.
Who should buy ATX
- Anyone building a general-purpose or gaming desktop in a mid-tower case, with no need to keep the PC small.
- Builders who want three or more M.2 drives, extra PCIe cards or plenty of fan headers.
- First-time builders, because there is more room to work and fewer clearance problems to plan around.
Consider Micro-ATX instead if you want to save money on a simple build or use a smaller case, Mini-ITX if small size is the point of the build, and E-ATX only if a specific flagship or workstation board requires it. ATX vs Micro-ATX vs Mini-ITX compares the three main sizes side by side.
What to look for when buying
- The socket and chipset first. Size is the second decision. See how to choose a motherboard.
- The slot layout, including how many slots remain usable once a thick graphics card is fitted.
- M.2 count and position, and which slots share lanes with SATA ports or PCIe slots. The manual lists this.
- Front-panel headers that match your case, such as a USB-C header.
- On open-box boards, the rear I/O shield where it is a separate part, the M.2 screws and the WiFi aerials.
Compare current prices on the ATX motherboard deals page, or see which boards have fallen furthest on price drops.
Questions people ask
What size is an ATX motherboard?
305 × 244 mm, or 12 × 9.6 inches. Some budget boards sold as ATX are the full height but a little narrower; they still fit any ATX case.
Will an ATX motherboard fit a Micro-ATX case?
No. An ATX board is taller than a Micro-ATX case allows. It works the other way round: a Micro-ATX or Mini-ITX board fits an ATX case, because the smaller sizes reuse the same mounting holes.
Is ATX better than Micro-ATX for gaming?
Not in itself. A Micro-ATX board with the same chipset and comparable power delivery runs a processor and graphics card just as fast. ATX gives you more slots, more M.2 positions and an easier build, not more speed.
How many PCIe slots does an ATX board have?
The specification allows seven slot positions, but most current boards fit fewer slots than that and use the space for M.2 drives. The number and the wiring of the slots vary by board, so check the specification.