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Rack Space Calculator

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Quick answer

Two power amplifiers, a processor, a digital snake, four wireless receivers, a power conditioner and one more item add up to 12U of gear. Add a vented rack unit above each amplifier and two spares for later, and the total comes to 16 rack units, which is a standard rack size.

Rack space planning fails in the same two ways every time: nobody leaves room for the heat an amplifier makes, and nobody leaves room for the next thing somebody buys. Both are cheap to fix on paper and expensive to fix after the rack is built and mounted.

Enter your gear list below. The calculator adds one vented rack unit above every amplifier automatically, adds two spare units on top, and rounds up to a rack size that is actually sold.

Rack space calculator

1U each, plus one vented U above every one.

1U each.

3U each, the usual size for a 16 or 32 channel box.

1U each unless yours are dual receivers sharing one space.

1U each, and it belongs at the top of the rack.

Direct box panels, patchbays, distribution amplifiers.

Rack size needed

16U

Racks, power conditioners and processors for this list

Top matches update when you change your numbers.

How is rack space calculated?

Three numbers add together:

  • Gear, the sum of every item's rack units times how many you have.
  • Vents, one open rack unit above every amplifier, non-negotiable. A class D amplifier still makes heat, and a rack packed solid with no airflow is the single most common reason amplifiers fail early in a church booth that has no climate control of its own.
  • Spares, two rack units held open for the next thing, because something always gets added: a second wireless channel, a feedback suppressor, a stage box.

The total is then rounded up to a rack size that is actually manufactured, so the answer is something you can order rather than a number you have to round yourself.

Rack size by amplifier count

Holding everything else constant at a processor, a digital snake, two wireless receivers, a power conditioner and one other item, and varying only how many power amplifiers are in the rack.

Two power amplifiers alongside a processor, a digital snake, two wireless receivers and a power conditioner needs a 14U rack once the vented space above each amplifier is included, and eight amplifiers push the same baseline gear to a 30U rack.

Rack size by number of power amplifiers, fixed baseline gear
AmplifiersGearVented unitsTotal neededRack size
19 U1 U12 U12 U
210 U2 U14 U14 U
311 U3 U16 U16 U
412 U4 U18 U18 U
614 U6 U22 U24 U
816 U8 U26 U30 U

Vented units grow one for one with amplifier count, which is why a rack with several amplifiers eats space far faster than the amplifiers themselves suggest.

Rack size by total gear, fixed at two amplifiers

Holding the amplifier count at two and varying the rest of the gear list, to show how the two spare units interact with standard rack sizes.

Sixteen units of other gear with two amplifiers needs a 24U rack rather than an 18U one, because the two spare units push the total past the next standard size rather than landing just inside it.

Rack size by total other gear, with two amplifiers
Other gearTotal neededRack size
4 U10 U10 U
8 U14 U14 U
12 U18 U18 U
16 U22 U24 U
20 U26 U30 U
24 U30 U30 U

This is the reason to build the gear list before buying the rack rather than after: a total that lands one or two units past a standard size wastes a whole size tier.

What actually goes in a church AV rack

A typical installed rack holds a power conditioner such as the Furman Power Conditioner, Black (M-8S) at the top for visibility and a clean power-up sequence, one or more amplifiers such as the Crown XLS1502 2-Channel Class D DriveCore Professional Power Amplifier with DSP, Band Pass Filters & Peak Limiters. XLR/RCA Inputs, 525W at 4 Ohm, PureBand Crossover System. Black or a 70 volt amplifier like the Crown CDi 1000 Two-Channel, 500-Watt @ 4Ω, 70V/140V Power Amplifier, a loudspeaker processor such as the dbx DriveRack PA2 2x6 PA Complete Professional Loudspeaker Management System, Rack Mountable with Android and iOS Control. Black, a digital stage box such as the Behringer S16 16-Channel Digital Snake Black if the console lives more than about thirty feet away, and a tray of wireless receivers. Housed in a case like the Gator Cases Pro Series 12U Rack Case, Standard 19" Depth (G-PRO-12U-19) for a closet install or the Gator Cases Content Creator Series Wooden Studio Rack Case with 15.25" Rackable Depth, 12U (GR-STUDIO-12U) where the rack sits visibly in the room.

Once the rack is sized, check the circuit it plugs into with the power draw calculator: a rack that fits physically can still be more amperage than one outlet is allowed to carry.

Frequently asked questions

How many rack units do I need for a church sound rack?

Add up the rack units of everything on the list, add one vented unit above every amplifier, add two spare units for whatever gets bought next, then round up to a size that is actually sold. A common small system with two amplifiers, a processor, a digital snake and a handful of wireless receivers lands around 14 to 16 rack units.

Why does an amplifier need a vented rack unit above it?

Amplifiers make heat even in class D designs, and a rack packed with no airflow traps that heat between components. An open vented unit above every amplifier is the cheapest insurance in the whole rack, and skipping it is the single most common reason an amplifier shuts down mid-service or fails years early.

How much spare rack space should a church leave?

Two rack units, as a baseline. Something always gets added within a year or two: a second wireless channel, a feedback suppressor, a stage box for a new campus feed. Leaving no spare space means the next purchase forces a rack swap rather than a simple addition, which costs far more than the two units would have.

What size rack case should I buy?

Round your total needed units up to a size that is actually manufactured: 6, 8, 10, 12, 14, 16, 18, 20, 24, 30, 36 or 44 are the common sizes. Buying the exact total you calculate, if it falls between two sizes, wastes the smaller size and forces an immediate second purchase. Buy the next size up.

Does a digital stage box change the rack space calculation?

Yes, by three rack units in a typical case, and it usually replaces a large amount of copper snake and a stage-side rack rather than adding to the booth rack alone. Factor the stage box into the booth side even though its counterpart, the console, may sit on a desk rather than in the rack.

Should wireless receivers go in the same rack as the amplifiers?

Usually yes, for cable management, but keep them physically separated from the amplifiers where the layout allows, since amplifier heat and amplifier-generated electrical noise are both things a sensitive wireless receiver front end would rather avoid. Where the rack is tight, put the receivers at the top and the amplifiers with their vented units at the bottom.

Researched, not professional advice. This page is compiled from published manufacturer specifications, operator manuals, FCC rules, published standards and owner-review consensus, not hands-on testing. Sound system design, rigging loudspeakers overhead, and any electrical work are jobs for a qualified professional: have flown loudspeakers and their attachment points signed off by a structural engineer or a certified rigger, and have all wiring done by a licensed electrician to your local code. Wireless microphone rules change, so confirm the current FCC position before buying. As an Amazon Associate we earn from qualifying purchases.