MRCOOL Sizing & Multi‑Zone Builder (Dynamic IDs)
Mini‑Split Sizing & Multi‑Zone Builder
Pick single room or build a multi‑room system. This is a rule‑of‑thumb tool; for precise design, request a Manual J.

How to Use the MRCOOL DIY Builder

  1. Enter Length and Width in feet. We auto-calc sq/ft and show the recommended single-zone BTU.
  2. Choose your series:
    • ESTAR Series (Best) — 9k–36k. Line sets: 25′, 41′, 50′, 60′, 75′.
    • EZPRO (Better) — 9k–24k. Line sets: 16′, 32′, 41′, 51′, 66′.
  3. Select the line-set length and click Add to cart. We send the exact variant automatically.

Tip: Near size breakpoints, we lean slightly larger for DIY comfort and future proofing.

  1. Click Add room and enter each room’s size. The tool suggests a head size (6k–36k) for each zone.
  2. Pick Wall Mount or Ceiling Cassette per room (mix & match), then choose the line-set length.
  3. We auto-bundle the correct pre-charged line set and matching control wire based on your length. Air handlers include a 25′ control wire; longer line sets auto-add the proper wire.
  4. The builder recommends a condenser that fits zones & BTUs (with a safe +6k head allowance). Oversize prompts include an override.
  5. Click Add full bundle to cart for a one-click kit.
  • Single-zone: 1 indoor air handler + 1 outdoor condenser/heat pump.
  • A refrigerant line set connects the two and circulates refrigerant.
  • The control wire runs with the line set and powers the indoor unit—no second circuit needed.
  • MRCOOL DIY ships pre-charged (indoor, outdoor, and line sets). You mount and connect.
  • Provide power to the outdoor condenser:
    • 9k & 12k single-zone: 120V
    • Other single-zone & all multi-zone: 220–240V

For the most accurate sizing, consider a Manual J load calculation.

  • Disconnect & whip: Usually required by code; purchased separately.
  • Outdoor mounting: Composite pad, gravel, concrete slab, wall bracket, or stand—keep level and maintain clearances.

MRCOOL DIY Mini-Split BTU Calculator & Multi-Zone Builder

Size your room(s) in minutes and build the perfect MRCOOL DIY mini-split system. Our BTU calculator recommends the right condensers, wall mounts or ceiling cassettes, and pre-charged line sets—then lets you add the whole bundle to cart.