Mini-split line set size chart
The quick reference for ductless line set sizing — diameter by BTU and by brand, plus standard lengths. Want it done for you? Use the size calculator or look it up by brand.
Line set size by mini-split capacity
Line set diameter is set by your system's BTU rating. Match the pair below, then pick your length.
| System size | Line set (liquid × suction) | Shop |
|---|---|---|
| 9,000 BTU (¾ ton) | 1/4" × 3/8" | Shop → |
| 12,000 BTU (1 ton) | 1/4" × 1/2" | Shop → |
| 18,000 BTU (1.5 ton) | 1/4" × 1/2" | Shop → |
| 24,000 BTU (2 ton) | 3/8" × 5/8" | Shop → |
| 36,000 BTU (3 ton) | 3/8" × 5/8" | Shop → |
| 48,000 BTU (4 ton) | 3/8" × 5/8" (some 3/8" × 3/4") | Shop → |
Line set size by line size
Already know your diameters? Here's what each stocked pair fits.
| Line set | Fits these systems | Shop |
|---|---|---|
| 1/4" × 3/8" | 9,000 BTU | Shop → |
| 1/4" × 1/2" | 12,000–18,000 BTU | Shop → |
| 3/8" × 5/8" | 24,000–36,000 BTU (and most 48,000 BTU) | Shop → |
Line set lengths
Length is set by the distance between your indoor head and outdoor condenser. Measure the full routing path — including bends and the drop — then round up to the next stocked length.
| Length | Best for |
|---|---|
| 15 ft | Short runs — same room or just through the wall |
| 25 ft | The most common length — typical wall-to-condenser runs |
| 35 ft | Longer runs, second-story, or units around a corner |
| 50 ft | Maximum reach — distant condenser placement |
On pre-charged DIY systems, watch the maximum pre-charged length (often 25 ft) — longer runs may need refrigerant added by a pro.
Line set size by brand
Diameter is the same across brands for a given capacity — what changes is the connection. Pre-charged quick-connect systems (like MrCool DIY) use proprietary line sets; everything else is field-flared. Look up your exact brand →
These are the most common pairings; exact diameters and the maximum line length are always printed in your unit's installation manual — treat it as the final word.
Common questions
What size line set for a 12,000 BTU mini-split?
A 12,000 BTU (1-ton) mini-split typically uses a 1/4" liquid line and a 1/2" suction line — 1/4" × 1/2". Confirm against your unit's manual, since some 12,000 BTU models use 1/4" × 3/8".
What are the standard mini-split line set sizes?
The most common ductless line set sizes are 1/4" × 3/8", 1/4" × 1/2", and 3/8" × 5/8" (liquid × suction), sold in standard lengths of 15, 25, 35, and 50 feet.
This chart provides general guidance based on common mini-split line set sizing. Exact line diameters, connection types, and maximum line lengths vary by model — always verify against the manufacturer's installation manual before purchasing or installing.