Refrigerant Capillary Tube Calculator

Created by Joanna Śmietańska, PhD
Reviewed by Steven Wooding
Last updated: Jun 05, 2023

Check our refrigerant capillary tube calculator to adjust your capillary copper tube for the refrigerator or air conditioner. The refrigerant capillary tube plays an important role in cooling systems and is easy to service. The difference in pressure from the refrigerant source in any refrigeration or cooling appliance means that you have to adjust the current capillary tube system, to maintain operating capacity.

With this useful calculator, find out the following:

  • What is a capillary tube?
  • How the capillary tube works in the refrigerator.
  • How to cool your device correctly and safely.

What is a capillary tube?

The capillary tube is a copper tube for refrigeration with a very small internal diameter. It has a very long length (1-6 m) and is rolled up to several turns to take up less space.

Typically, the internal diameter of the capillary tube used in refrigeration and AC applications ranges from 0.50 to 2.28 mm (0.020-0.09 in). This diameter of a circle calculator will help you to find the inside diameter of the capillary tube and much more.

You can select different hole and length combinations to achieve the desired performance. Capillary tubes are only used in hermetically sealed systems because there is no risk of refrigerant leakage. It is important to note that once you have selected and installed a capillary tube, you cannot change the load conditions.

To maintain efficiency under varying conditions, you must select a new capillary tube with a different size. This is where our refrigerant capillary tube calculator comes in handy so that you can do it in a snap!

How the capillary tube works in the refrigerator?

The capillary tube is the key component that separates the high-pressure zones and the low-pressure side of the refrigeration system. There we have two areas: the receiver (containing liquid refrigerant at high pressure) and the evaporator (containing liquid refrigerant at low pressure).

A capillary tube connects them and condenses the amount of refrigerant supplied to the evaporator. Check out the pressure calculator if you want to learn about pressure.

When the high-pressure liquid refrigerant enters the refrigerant capillary tube, its pressure drops down suddenly due to the very small diameter of the capillary. In addition, it helps to maintain the desired pressure difference between the high and low-pressure sides of the system.

So that the liquid refrigerant evaporates in the evaporator at the selected pressure, finally, the capillary tube controls the flow of refrigerant depending on the evaporator load.

Refrigerant capillary tube resizer – formula

The dimensions of the capillary tube are connected by the formula below:

NL=OL×(New ID/Orig ID)4.6,\footnotesize{\mathrm{NL = OL \times (New\space ID/Orig\space ID)^{4.6}}},


  • NL\rm NL – New length of the capillary;
  • OL\rm OL – Original length of the capillary tube;
  • New ID\rm New\ ID – The new inside diameter of the tube you need; and
  • Orig ID\rm Orig\ ID – The original inside diameter of the capillary tube.

How to use refrigerant capillary tube calculator?

To use our refrigerant capillary tube calculator, simply enter the following data:

  1. Measure the original inside diameter of your capillary tube and type it into the "Original ID" field.

  2. Specify the original length of the tube and type it into the "Original length" field.

  3. Determine the new inside diameter of the tube that will be useful to you and enter it into the "New ID" field.

  4. Congratulations! You have calculated the length of the new tube you will need.

Feel free to specify the dimensions of the refrigerant capillary tube that you know. You don't even know what the refrigerant capillary tube resizer formula is in the first place! Just enter any three sizes and our refrigerant capillary tube calculator will help you determine the fourth, unknown size.


What is a capillary tube in refrigeration?

A capillary tube controls the refrigerant flow into the evaporator and reduces the pressure. It is usually a long copper tube with a diameter of 0.5 to 2.5 mm and a length of 1 to 6 m.

How can I choose a capillary tube for refrigeration?

When you are looking for a copper tube for refrigeration, you should consider the capacity of the condenser system and the inner diameter of the tube. Avoid choosing a capillary that is too long or too short. A capillary that is too short is more prone to deflection and bending stress. A capillary that is too long will lead to excessive pressure.

What are the most common causes of a capillary tube failure?

Capillary tubes tend to be clogged because refrigerant flows through an extremely small hole at the end of a long pipe. Always remember about a proper maintenance plan to prevent accumulation of dirt or overheating of the system.

How can I fix blocked capillary tube in refrigerator?

Below you will find a brief solution to the most common problems associated with a blocked capillary tube:

  1. If the capillary tube is clogged, use lubricants or chemicals that will dissolve the impurities.

  2. Use a heavy-duty pipe cleaner or screwdriver to unclog debris and dirt.

  3. Melt the ice accumulated on the capillary tube with a hot towel.

  4. Replace the filter to remove the wax from a combination of dirt, debris, and moisture.

  5. Heat the entrance to the capillary tube to remove the oil.

What will be the new length of 3.5 m of tube if I change its diameter from 1.5 to 1.3 mm?

The new length is 1.81 m. Divide the original and new inside diameters by 1000 to obtain the size in meters.

Enter the original length of 3.5 m, an original inside diameter of 0.0015 m, and a new inside diameter of 0.0013 m into the equation:

new length = original length × (new inside diameter/original inside diameter)4.6

new length = 3.5 m × (0.0013 m/0.0015 m)4.6 = 1.81 m.

Joanna Śmietańska, PhD
Original ID
Original length
New ID
New length
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