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A 12×12 bedroom (144 sq ft) typically needs 3,600–4,300 BTU calculated — retail mini-splits start at 9,000 BTU. Enter your exact dimensions below for cooling load, heating estimate, and recommended ductless head size.

BTU & Mini-Split Calculator

Enter room dimensions. Get cooling BTU, heating estimate, and recommended mini-split size.

Space dimensions

ft
in
ft
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ft
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Sizing settings

Application
Insulation
Sun exposure
Climate

Your sizing estimate

Enter space dimensions to see BTU load and recommended mini-split size.

Mini-split sizing by application

Pre-set insulation and load factors for RVs, tiny homes, backyard sheds, and seasonal cottages.

DIY sizing guides

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RV installs, tiny home insulation, she-shed comfort, cottage heat pumps, and mini-split mistakes to avoid.

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Mini-Split Sizing for Tiny Homes — BTU & One-Head Plans

Size ductless AC and heat pumps for 200–400 sq ft tiny houses. Loft ceilings, galley kitchens, and THOW air leakage factors.

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Insulating a Tiny Home for HVAC — Before You Size AC

Spray foam, rigid board, and air sealing for tiny houses. Why insulation cuts BTU load and prevents condensation in small envelopes.

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RV & mobile

What Size Mini-Split for an RV? — BTU by Length & Layout

Mini-split BTU sizing for travel trailers, fifth-wheels, and skoolies. Thin walls, windows, and full-time hot-climate living.

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RV Mini-Split Installation Options — Mounting & Power

Condenser on hitch rack, bumper mount, or roof bracket. Line sets, vibration, and shore power for DIY RV ductless installs.

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How it works

  1. 1. Measure your spaceEnter length, width, and ceiling height for each room, RV living area, or shed footprint.
  2. 2. Set application typeChoose RV, tiny home, she-shed, cottage, or standard room — insulation and BTU factors adjust automatically.
  3. 3. Buy the right BTUWe calculate cooling load, heating estimate, and round up to common mini-split sizes (9k, 12k, 18k, 24k).

FAQ

How many BTU per square foot?

Most cooled rooms need 20–30 BTU per sq ft. RVs and uninsulated sheds need more; well-insulated tiny homes need less. Sun exposure, ceiling height, and occupants adjust the result.

What size mini-split for an RV?

Most full-time RVers use 9,000–12,000 BTU depending on length and insulation. A 30 ft RV with 200–250 sq ft of living space often needs a 9k minimum; 12k is common in hot climates.

Can I size a whole tiny home with one calculator?

Yes — add up to five spaces or enter the main living footprint as one zone. Most tiny homes use a single 9k–18k BTU ductless head.

Is this a Manual J calculation?

No. This is a DIY planning tool. For permits and whole-house central HVAC, hire a licensed pro for Manual J and Manual S equipment selection.