Theres no need to purchase dowels specifically to measure a garden hose. Simply run the tape measure from the top of your hoses opening to the bottom and record its diameter.

Automotive Fittings Explained
How to measure hose fitting size. If you dont have dowels on hand use other objects such as high speed metal drill bits. Allow the tube to open until the edges. Allow approximately half of the tube to. If the centrelines of the connection and gauge are parallel the correct angle has been determined. A tape measure is the best way to measure your personal garden hoses size. How to measure garden hose diameter.
Try a 58 inch wooden dowel and a 34 inch dowel until you find the size that has the best fit. Wrap a string around the pipe. Roll an index card into a tube like a straw and insert one end into the open end of the garden hose. Remove the spray nozzle or any other attachments to your garden hose. Insert a 12 inch wooden dowel into one end of the hose and check the fit. Use a ruler or measuring tape to find the length between the tip of the string and the mark you made circumference divide the circumference by 314159.
Use these guides when identifying hydraulic fittings including drawings dimensions and connection instructions for bsp sae npt and more. Measure the outside diameter od of your pipe or pipe fitting. When measuring the number should refer to the internal diameter as this is size that needs to match the garden hose to a fitting nozzle or faucet. Mark the point where the string touches together. Male flare type connectors are usually measured by placing the gauge on the sealing surface. Female connections are usually measured by inserting the gauge into the connection and placing it on the sealing surface.