Refrigerant Capillary Tube Resizer
Calculate the new length or inner diameter of a refrigerant capillary tube using the formula NL = OL × (New ID / Orig ID)⁴·⁶. Free online HVAC capillary tube sizing tool with charts and breakdowns.
Formula: New Length = Original Length × (New ID / Original ID)4.6
About This Calculator
The Refrigerant Capillary Tube Resizer Calculator helps HVAC technicians, refrigeration engineers, and appliance repair professionals determine the correct capillary tube dimensions when replacing or modifying a refrigeration system. When you change the inner diameter of a capillary tube, its length must be adjusted using the formula NL = OL × (New ID / Orig ID)4.6 to maintain the same refrigerant flow rate and system cooling capacity.
A capillary tube is a long, narrow copper tube used as a fixed-restriction expansion device in small to medium refrigeration systems such as household refrigerators, freezers, window air conditioners, and dehumidifiers. It connects the high-pressure condenser side to the low-pressure evaporator side, creating a pressure drop that allows the liquid refrigerant to expand and cool before entering the evaporator coils. Typical capillary tubes have inner diameters from 0.5 mm to 2.28 mm and lengths from 1 to 6 meters.
Our calculator supports computing any of the four parameters — original length, original inner diameter, new length, or new inner diameter — by entering the other three values. Select what you need to calculate from the dropdown, fill in the known dimensions, and get instant results with a comparison chart and detailed breakdown table.
How to Use
- Measure the original capillary tube length and inner diameter using appropriate tools (tape measure and pin gauge or micrometer).
- Enter the original dimensions into the calculator.
- Enter your target dimension — either the new inner diameter (if you want to use a tube with a different bore) or the new length.
- Select which value to calculate from the dropdown and click Calculate.
- Review the computed result, the diameter ratio, and compare original vs new dimensions using the bar charts.
Frequently Asked Questions
What is a refrigerant capillary tube?
A refrigerant capillary tube is a long, narrow copper tube with an inner diameter of 0.5 to 2.28 mm and length of 1 to 6 m. It acts as a throttling device in refrigeration and air conditioning systems, creating a pressure drop between the condenser and evaporator to control refrigerant flow.
How does the capillary tube resizer formula work?
The formula NL = OL × (New ID / Orig ID)⁴·⁶ relates capillary tube length and inner diameter. When you change the tube diameter, the length must be adjusted by the diameter ratio raised to the 4.6 power to maintain the same refrigerant flow characteristics and cooling capacity.
How do I use the refrigerant capillary tube calculator?
Enter the original capillary tube length and inner diameter, then enter either the new inner diameter or new length. Select what you want to calculate from the dropdown, and click Calculate. The calculator will compute the missing dimension using the resizer formula.
What happens if I use the wrong capillary tube size?
A capillary tube that is too short may cause insufficient pressure drop, reducing cooling efficiency and potentially damaging the compressor. A tube that is too long can cause excessive pressure drop, starving the evaporator of refrigerant and reducing system capacity. Always use the correct diameter-length combination.
How do I measure the inner diameter of a capillary tube?
Use a precision pin gauge or a micrometer to measure the inner diameter of the capillary tube. Common sizes range from 0.5 mm to 2.28 mm (0.020 to 0.090 inches). For accurate results, measure at the cut end of the tube and average multiple readings.
Can I use this calculator for air conditioner capillary tubes?
Yes, this calculator works for refrigerant capillary tubes in air conditioners, refrigerators, freezers, and any vapor-compression refrigeration system that uses a capillary tube as an expansion device.
What common refrigerants work with capillary tubes?
Capillary tubes are compatible with R-134a, R-600a (isobutane), R-290 (propane), R-404A, R-410A, and R-22 refrigerants. The resizer formula is independent of refrigerant type — it only depends on tube geometry.