Zip Tie Size Chart: What Size Cable Tie Do You Need?

Every cable tie listing comes down to four numbers. Two of them decide whether the tie fits, and two decide whether it holds.

Length and max bundle diameter are about fit. Width and tensile strength are about load. A longer tie is not a stronger tie: strength comes from the width and thickness of the strap and the design of the locking head, so a 36 inch tie and an 8 inch tie of the same cross section carry roughly the same rating.

• Length: the overall length of the strap from the tip to the far side of the head, usually given in inches or millimeters. Listed lengths are often nominal, so a tie sold as 8 inch may measure slightly less.
• Width: the width of the strap. Wider straps generally carry higher ratings. Common widths run from about 0.10 inch (2.5 mm) on miniature ties to about 0.30 to 0.35 inch (7.6 to 9 mm) on heavy-duty ties.
• Loop tensile strength: the minimum force, in pounds, that a closed loop of the tie withstands in a pull test. It is a breaking-point rating, not a working load.
• Max bundle diameter: the thickest round bundle the tie can wrap and still lock with enough strap engaged in the head.

The chart below shows common lengths, the tensile classes they are most often made in, and an approximate max bundle diameter for each. Manufacturers publish exact bundle diameters on their spec sheets; the figures here are estimates we calculated from length so you can compare sizes at a glance.

The estimate works like this: take the nominal length, subtract about 1.5 inches for the head and the strap needed to engage it, and divide the rest (the loop circumference) by 3.14. For a 7.4 inch standard tie, that gives about 1.88 inches, which is in line with published figures for ties of that length. Heavy-duty ties have larger heads and may close around slightly less than the estimate.

Cable ties are sold in a handful of strength classes that most of the industry uses. The names are common shorthand rather than a formal standard, and some manufacturers add in-between classes (such as 30 lb or 75 lb), so always read the rated number on the package rather than the class name alone.

• Miniature: 18 lb. Narrow straps, usually 4 to 8 inches long.
• Intermediate: 40 lb. A step up for small bundles.
• Standard: 50 lb. The everyday electrical tie, often 8 to 14 inches.
• Heavy duty: 120 lb. Wider straps for heavier bundles and outdoor work.
• Extra heavy duty: 175 lb. Common in longer lengths such as 24 and 36 inches.
• 250 lb: the top of the typical nylon range, used for the largest bundles and heaviest nylon applications.

Measuring takes a minute and saves buying the wrong bag. You need a flexible tape, a piece of string or a strip of paper.

1. 1Wrap the tape or string around the thickest point of the bundle, pulling it snug the way the tie will.
2. 2Read the circumference. If you used string, mark it and measure it flat.
3. 3Divide the circumference by 3.14 to get the bundle diameter.
4. 4Find a tie whose max bundle diameter is larger than your number. Leave margin if the bundle will grow, if you are wrapping two objects together, or if you are going around a post or rail.
5. 5Check the tensile rating against the load, then choose black UV-stabilized ties if the tie will see sunlight.
6. 6Fit one tie before you commit to a full job. You want several ratchet teeth engaged in the head, not the very tip.

Our nylon ties are 100% PA66 in the lengths and strengths below. We do not yet publish a measured max bundle diameter for our products, so the third column uses the same approximate calculation as the chart above. Colors vary by size and brand, so check each product page for Black (UV-stabilized, for outdoor use) or Natural Clear White (for indoor and general-purpose use).

When a bundle falls between sizes, a slightly longer tie is almost always the better choice. You can trim the tail; you cannot stretch a short tie.

• Go longer when the bundle may grow later, when you are wrapping around a post, or when you are wearing gloves and need extra strap to grab.
• Go stronger, not just longer, when the load is heavy, the job is outdoors, or the tie will see vibration. Length does not add strength.
• Trim tails flush with a flush cutter or tie tool. A tail cut at an angle leaves a sharp edge that can scratch hands and cable jackets.
• Standardize on a few sizes. A short tie, a 12 inch heavy-duty tie and a long tie cover a lot of everyday work.