What Is the AMPS Mounting Pattern? Hole Spacing, Compatibility & How to Use It
Flip over almost any vehicle phone holder, GPS cradle or radio bracket & you will find the same four holes.
Two rows. A small rectangle. Screws that seem to fit every mounting plate you've ever owned.
That is the AMPS mounting pattern, & it is the quiet reason the vehicle mounting world mostly plays nice together. If you've ever wondered why a Mountech base bolts straight onto a BuiltRight dash mount, or why a Garmin cradle fits a RAM plate, this is why.
What AMPS Stands For
AMPS is short for Advanced Mobile Phone System, the analog cellular network standard from the 1980s. Car phones of that era needed a cradle bolted into the vehicle, & the four-hole pattern used to attach those cradles outlived the network by decades.
The phones are long gone. The hole pattern stuck around because it worked, & because every accessory maker that adopted it made the next accessory maker's life easier.
Today "AMPS pattern," "AMPS hole pattern" & "AMPS mount" all mean the same thing: that four-hole rectangle.
The AMPS Hole Pattern Dimensions
The pattern is a rectangle with a hole at each corner. Those two numbers below are the whole standard.
Measuring tip: if a plate has four holes on those centers, it is AMPS compatible. Measure center to center on the holes, not edge to edge.
AMPS specifies hole positions, not plate size. An AMPS plate can be a compact square barely bigger than the pattern, or a large slotted bracket like the BuiltRight dash mounts, which use an AMPS-compatible slot pattern so you can slide a base to multiple positions.
What Uses the AMPS Mounting Pattern
A lot more than phones.
- Phone & tablet holders from nearly every mounting brand
- GPS cradles (Garmin & similar)
- Two-way radio & GMRS brackets
- Vehicle-specific dash mounts, including every BuiltRight dash mount
- Ball mount bases, including Mountech's 4-Bolt Base
- Fleet & ELD tablet docks in work trucks
Because both ends of the system speak the same pattern, you get real modularity. A dash mount with an AMPS pattern accepts any AMPS ball base. That ball base accepts any 1-inch ball arm. That arm accepts any holder with a 1-inch ball. Change one piece & the rest stays.
AMPS vs VESA vs 2-Bolt Plates
These three get confused constantly, so here is the difference.
AMPS
30 x 38 mm, four holes. The vehicle & device mounting standard. What this whole post is about.
VESA
75 x 75 mm & 100 x 100 mm. The monitor standard. Much larger, meant for displays, not interchangeable with AMPS without an adapter.
2-Bolt "diamond"
Two holes, compact, common on smaller ball bases. Not AMPS. Mountech's 2-Bolt Base exists for exactly these spots.
If you are shopping & a listing just says "universal," look for the hole pattern in the specs. Universal usually means AMPS. Sometimes it means nothing at all.
How to Check Whether a Holder or Base Is AMPS Compatible
Three quick checks.
- Count the holes. Four holes in a rectangle is the first sign.
- Measure the spacing. 30 mm one way, 38 mm the other, center to center. A tape measure is fine. Calipers are better.
- Read the listing. Most brands state AMPS compatibility outright because it is a selling point. Mountech lists it on the bases collection & on each base product page.
If the holes are there but the spacing is off by more than a millimeter or two, it is a proprietary pattern & you'll want an adapter plate.
Using AMPS With a 1-Inch Ball System in a Truck
This is where the pattern earns its keep. A typical Mountech install in a pickup goes like this:
Four parts. Every joint is a standard. Nothing is glued, clipped or stuck on.
It also works in reverse. If you already have an AMPS holder for a GPS or radio that you like, it will bolt to the top of the Mountech ball mount just as easily. The pattern doesn't care which direction you're going.
Quick Answers
What is the AMPS hole pattern?
A four-hole rectangular mounting pattern with holes on 30 mm x 38 mm centers. It is the most common standard for vehicle phone, GPS & radio mounts.
Is AMPS the same as VESA?
No. VESA is a larger monitor standard (75 x 75 mm & up). AMPS is 30 x 38 mm & used for device mounts.
Do all Mountech bases use the AMPS pattern?
The 4-Bolt Base & SpinLok 4-Bolt Ball Mount use AMPS. The 2-Bolt Base uses a two-hole pattern & the Direct Mount uses a single bolt, so you can match whatever surface you are mounting to.
If ball sizes are the other half of the puzzle for you, our RAM ball size guide covers the letter-to-inch conversions. And the Getting Started guide puts the whole base-arm-holder system in order.
Build on the standard
AMPS bases, 1-inch ball arms & device holders that work with what you already own.
