Straight Shank Taper Length Twist Drills Calculator has been developed by using drill bit size charts which are given in the ANSI B94.11M-1993 - "Twist Drills" standard. Calculator covers inch and metric size of straight shank taper length drill bit sizes .

Note: For more information on twist drills including nomenclature, definitions, sizes and tolerances of high speed steel, straight and taper shank drills, combined drills, countersinks, plain and bell type, please refer to pages 867 - 889 of Machinery's Handbook, 29th.


Drill Bit Unit System
Drill Diameter
Drill Diameter (D)


Straight Shank Taper Length Twist Drills
Parameter Symbol Value Unit
Selected Drill D --- ---
Equivalent diameter in inch --- in
Equivalent diameter in mm --- mm
Flute Length F --- inch
--- mm
Overall Length L --- inch
--- mm
Length of Body B --- inch
--- mm
Minimum Length of Shank S --- inch
--- mm
Maximum Length of Neck N --- inch
--- mm


Drill bits: Drill bits are tools to cut cylindrical holes on workpiece. Drill bits are generally used with drills to create a hole. The shank of the drill is holded by the chuck of a drilling machine.

Twist drill bits are generally produced from high speed steel (HSS), cobalt steel alloys and tungsten carbide. Coatings are applied to drill bits to extend the life of the bit. Black oxide, titanium nitride and titanium aluminum nitride are coatings which are generally applied to drill bits

Twist drills are rotary end-cutting tools having one or more cutting lips and one or more straight or helical flutes for the passage of chips and cutting fluids. Twist drills are made with straight or tapered shanks.

Jobber length drill bit: Straight shank drills suitable for general purpose applications.The length of the flutes is between nine and fourteen times the diameter of the drill.

Screw machine length drill bit: Drill bit set with shorter flute length than the average Jobbers. It’s rigid and better for drilling harder materials. Due to short length, shallower holes are drilled.

Taper length drill bit: Taper length drills are general purpose drills with increased cutting length. Taper length drills have same flute length as taper shank drills.

Straight Shank Drills: Those having cylindrical shanks which may be the same or different diameter than the body of the drill. The shank may be with or without driving flats, tang, grooves, or threads.

Taper Shank Drills: Those having conical shanks suitable for direct fitting into tapered holes in machine spindles, driving sleeves, or sockets. Tapered shanks generally have a driving tang.

  • Oberg.E , Jones.D.J., Holbrook L.H, Ryffel H.H., (2012) . Machinery's Handbook . 29th edition.  Industrial Press Inc. , pp 867 - 889
  • ANSI B94.11M-1993 - Twist Drills