Multi-Zone Mini-Split BTU Sizing & Condenser Match Calculator

Calculate heating and cooling BTU loads for up to 4 individual rooms, match indoor head unit sizes (7k–24k BTU), select outdoor multi-port condenser capacity, and verify connection diversity ratios (100%–130%).

Climate & Insulation Baseline

Climate Zone / Region

Home Insulation & Windows

Room / Zone Square Footage

Zone 1 (Living)

Zone 2 (Master Bed)

Zone 3 (Bed 2)

Zone 4 (Office/Guest)

Set any unused zone square footage to 0.

Ceiling Height

Outdoor Condenser Capacity

Preset Multi-Zone Configurations

Recommended Outdoor Condenser Optimal Diversity Ratio

3.0 Ton (36,000 BTU)

Connected head capacity: 37,000 BTU (102.8% connection ratio)

Total System Building Load

32,240 BTU/hr

1,040 sq ft total conditioned area

Active Indoor Head Count

4 Head Units

Requires 4-Port Multi-Split Condenser

Recommended Indoor Head Unit Sizes

Zone 1 (450 sq ft): 15,000 BTU (Match: 15k or 18k Head)

Zone 2 (250 sq ft): 9,000 BTU Head

Zone 3 (180 sq ft): 7,000 BTU / 9,000 BTU Head

Zone 4 (160 sq ft): 7,000 BTU / 9,000 BTU Head

Frequently Asked Questions

What happens if I connect 36,000 BTU of heads to a 30,000 BTU condenser?

This represents a 120% connection ratio, which is fully supported and recommended by major manufacturers. The variable-speed inverter compressor automatically redistributes refrigerant where demand is highest. If all heads run at maximum, the condenser delivers its rated 30,000 BTU distributed proportionately.

Should I install one 4-zone condenser or two 2-zone condensers?

Installing two separate 2-zone condensers often provides higher partial-load SEER2 efficiency, shorter line-set piping runs, lower turndown minimums (preventing short-cycling in small bedrooms), and built-in redundancy if one unit ever needs service.