Hydraulic hoses are essential equipment. They help transport the fluid and can even withstand harsh pressure with ease. However, hydraulic hoses are available in a range of sizes, typically specified in either inches or millimeters. This raises a question: How to convert MM to inches?
This conversion looks pretty technical and related to boring mathematics. So, many people in the hose industry use the MM-to-Inch conversion charts. Interestingly, this conversion is straightforward to do if you have the basics right. In this article, I will discuss this conversion so you know how to convert millimeters into inches. So, let’s get started!
Why Right Hydraulic Hose Size Matters?
Before discussing conversion, let’s first understand why hydraulic hose size is essential. Hydraulic hoses are typically used in heavy-duty machines. Their role is to carry high-pressure hydraulic fluid to the cylinder. If the hydraulic hose size is smaller, it won’t transfer enough hydraulic fluid to the cylinder.
The hydraulic system’s efficiency will be significantly reduced. In some cases, if hydraulic fluid is under very high pressure, it can even damage a smaller hose. Similarly, if the hydraulic hose is larger than needed, it can reduce the fluid pressure. In simple terms, the right-sized hydraulic hose ensures smooth pressure throughout the system.
As a result, the hydraulic system operates smoothly, allowing machinery to run without safety issues. For both sellers and buyers, knowing the right hose size is essential. Small mistakes in hydraulic hose size can lead to serious consequences. The size of hoses (all types) is generally shown in either inches or millimeters. That’s why understanding the conversion of these units is critical.
What are MM and Inches?
Both inches and millimeters are units of length used in different parts of the world.
Millimeter (MM) is the length unit in the metric system and is used in Europe and Asia. On the other hand, an inch is a unit of length, but it is primarily a US system unit used in the USA. One inch is equivalent to 25.4 millimeters. Similarly, one millimeter is equal to 0.03937 inches. The hose you buy can be measured in inches or millimeters, depending on where it’s made.
Manufacturers use these inches and millimeters to represent the internal diameters of the hoses. Remember, hydraulic hoses are made worldwide. So if they are manufactured in the USA, their inner diameters would be mentioned in inches. Conversely, if made in Europe, the size of hoses would be in millimeters (MM). Modern manufacturers use fractions to indicate hose sizes.
How to Convert MM into Inches?
You can convert the MM into inches with the following formula:
Inch = Millimeters / 25.4
So, suppose you have a hydraulic hose with an internal diameter of 6 mm. You can easily calculate its ID in inches in the following way:
Inch = 6 / 25.4 = 0.236 inches
This means your hydraulic hose has an ID of 0.236 inches. In the fraction system, this size can also be represented as ¼ inches. Remember, manufacturers generally use a fractional system to represent the size. However, you can convert the fraction to a decimal and determine the exact ID of the hydraulic hose. Suppose you see a hose with a ⅜-inch size. This means that the hose has an ID of 0.37 inches in decimal notation and ⅜ in fractional notation.
How to Convert Inches into MM?
Converting inches into millimeters is easy using the following formula:
Millimeters (MM) = Inches × 25.4
Suppose you have a hydraulic hose with a size of 0.25 inches. In this case:
Millimeters (MM) = 0.25 × 25.4 = 6.35 mm
This means your hydraulic has an internal diameter of 6.35 mm. Remember, sometimes you’ll see sizes written such as ⅝ or ⅜ inches. This can be confusing since you don’t get an exact value to multiply by 25.4. In such a case, you’ll first convert the fractional numbers into decimal form and then use the above-given formula. For example, for a hose with ⅝ inches in size:
Conversion of a fraction to a decimal
5 ÷ 8 = 0.625 inches
This is a decimal form which you can put into the formula to find the exact millimeters:
Millimeters (MM) = 0.625 × 25.4 = 15.88 mm
Do the same for the ⅜-inch hydraulic hose.
3 ÷ 8 = 0.375 inches
Millimeters (MM) = 0.375 × 25.4 = 9.52 mm
You can use this method to convert any size (in inches) to millimeters. In the above calculations, I used an assumed value. You will only change these values based on the size of your hose and perform the calculations. However, if you want to avoid these calculations, you can also use the MM to inches conversion chart.
Millimeters to Inches Conversion Table
Here is a table for quick conversion of millimeters to inches:
| Millimeters (mm) | Decimal Inches | Fractional Inches (Approx) |
| 6 | 0.236 | 1/4 in |
| 8 | 0.315 | 5/16 in |
| 9 | 0.354 | 3/8 in |
| 10 | 0.394 | 3/8 in |
| 12 | 0.472 | 1/2 in |
| 16 | 0.630 | 5/8 in |
| 19 | 0.748 | 3/4 in |
| 25 | 0.984 | 1 in |
| 32 | 1.260 | 1 1/4 in |
| 38 | 1.496 | 1 1/2 in |
| 50 | 1.968 | 2 in |
How Do You Know the Right Hose Size for Your System?
Each hydraulic system has different hose size requirements. For example, systems are used for heavy-duty motors. In such cases, they move more hydraulic fluid at very high pressure. In such a case, you’ll need a hydraulic hose with a larger internal diameter. On the flip side, there are hydraulic systems that don’t involve intense pressure. In such cases, using smaller-diameter hoses will work fine.
However, the exact hose size you need depends on the fittings in your system. I recommend using a measuring device to measure the inside diameters of both fittings and hoses. You should choose a hose size (ID) that fits the hydraulic fitting. If the hydraulic fitting and hose size are in different units, don’t worry. You can use the above formula to convert the hose and fitting sizes to the same unit, then choose the correct size.
Frequently Asked Questions
Can I use a 12 mm hose instead of a 1/2 inch hose?
Yes, you can use a 12 mm hose instead of a 1/2-inch hose. These two hoses are almost the same size, which fits their use cases, especially in hydraulic hose systems.
Do all hoses of the same ID have the same pressure rating?
No. Different hoses have different pressure ratings. Two hoses with the same ID and other materials can have different pressure ratings. This rating depends primarily on the material and quality of those hoses.
What happens if I choose the wrong hydraulic hose size?
Using the wrong-sized hydraulic hoses can be a bad idea. Why? That’s because it can affect the working and efficiency of the hydraulic system. A lot of people don’t handle high pressure. Similarly, a larger hydraulic hose will reduce pressure, potentially causing issues with the hydraulic system.
Conclusion
Let’s wrap this up – hydraulic hoses are handy and make large machines work efficiently. However, if you use the wrong size of these hoses, their performance can be affected. As a result, the machinery with a hydraulic hose system may not operate efficiently. Therefore, you must choose a hydraulic hose compatible with your system.
In choosing the right size, it is crucial to understand MM-to-inch conversions. The reason is that some manufacturers use MM to represent the hose ID. You’ll also see that inches are a representation of the unit length of the hoses. In this article, I have discussed the MM-to-inch conversion with a detailed explanation.