Fid Lengths & Measurements

Fids are one of the most important tools utilized in the splicing of rope. Through the ages, fids have been made from bone, wood, plastic and steel in the form of wire, tubes and rods. While they are often used as measuring devices, the main purpose of a fid is to allow the user a means to manipulate the strands of a rope in order to complete a splice. 

The term “Fid length” in our splicing instructions always refers to a “full fid length” which is generally accepted to be 21 times a rope’s diameter. If you intend to use a fid as the basis for your measurements while splicing rope, it is always a good idea to double check your measurements with a measuring tape. For your convenience, the following table provides measurements for short, long and full fid lengths.

 Approximate ratios – Short Fid* 1:7* – Half Fid 1:10.5 – Long Fid 1:14 – Full Fid 1:21

*Short fid lengths are often calculated as a percentage of the total fid length as opposed to using 7 times the diameter or 1/3 the length of the fid.

  • Smaller ropes up to ½” inches in diameter, have short fid lengths calculated to 37.5% of the total length of the fid.
  • 9/16″ to 3/4″ diameter rope have short fids lengths calculated to approximately 30% of the total length of the fid.
  • 7/8″ diameter and up have short fid lengths calculated to approximately 25% of the total length of the fid.

Fid Length Table

ROPE DIAM. IN
Ø “
SHORT FID
(IN.)
LONG FID
(IN.)
FULL FID
(IN.)
3/32″ 3/4″ 1-5/16″ 2″
1/8″ 1″ 1¾” 2⅝”
3/16″ 1½″ 2⅝” 4″
1/4″ 2” 3½” 5¼”
5/16″ 2½″ 4⅜” 6-9/16″
3/8″ 3” 5¼” 7⅞”
7/16″ 3½″ 6⅛” 9-3/16″
1/2″ 4” 7″ 10½”
9-16″ 4¼″ 7⅞” 12″
5/8″ 4½″ 8¾” 13⅛”
11/16″ 4-13/16″ 9⅝” 14-7/16″
3/4″ 4-3/4” 10½” 15¾”
7/8″ 4½” 12¼” 18⅜”
1″ 5¼″ 14″ 21″
1⅛” 6” 15¾” 23⅝”
1¼” 6½” 17½” 26¼”
1-5/16″ 7″ 18⅜” 27-9/16″
1½” 8” 21″ 31½”
1⅝” 8½” 22¾” 34⅛”
1¾” 9¼” 24½” 36¾”
2″ 10½″ 28″ 42″