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Pi Tape® Precision Diameter Measuring Tapes

What is a Precision Diameter Measuring Tape?

It is a measuring tool to measure the diameter of a cylindrical object.

It simply takes a precision standard measurement and divides it by π ( pi )


The periphery tape. exemplified by Pi Tape® brand tape, provides a quick, accurate and easy method of reading true diameters of both round and out-of-round forms.

  • Perfect for measurement of thin or soft walled parts - large or small.

  • Pi Tape gages consist of a narrow metal ribbon bearing special graduations.
    These graduations are designed to convert circumferential distance into diameter measurement so the observer can read the diameter directly from the scale.

  • Tapes are checked over master gages at .001'"(.03mm) accuracy for standard tapes up to 144" (3600mm).
    Certificate of accuracy traceable to National Institute of Standards and Technology is furnished.

  • Pi Tape gages are a precision tool made of 1095 clock spring steel (on request 420 stainless steel - for use in a corrosive atmosphere).
    They require a minimum of maintenance, but we do recommend a quick wipe with an oil moistened cloth after use. A light gun oil works very well.

Make sure the tape has not been dented or kinked. This may affect the accuracy of the tape.

Pi Tape gages are invaluable tools to the aero-space field as well as the plastic pipe industry. The variety of uses are infinite.

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In stock... tapes ranging from 3/4"-7" to 132"-144" diameter available for same day shipping.

Part No.

O.D,Outside Diameter Measuring Range


Standard Outside Diameter,

Material:    1095 Spring SteelClock Steel

PI-000 1/2-2" .500 to 2" Diameter Tape
PI-01 3/4-7" .75 to 7" Diameter Tape
PI-1 2-12" 2 to 12" Diameter Tape
PI-1SP 2-24" 2 to 24" Diameter Tape
PI-2 12-24" 12 to 24" Diameter Tape
PI-2SP 12-36" 12 to 36" Diameter Tape
PI-3 24-36" 24" to 36" Diameter Tape
PI-3SP 24-48" 24 to 48" Diameter Tape
PI-4 36-48" 36 to 48" Diameter Tape
PI-5 48-60" 48 to 60" Diameter Tape
PI-6 60-72" 60 to 72"Diameter Tape
PI-7 72-84" 72 to 84" Diameter Tape
PI-8 84-96" 84 to 96" Diameter Tape
PI-9 96-108" 96 to 108" Diameter Tape
PI-10 108-120" 108 to 120" Diameter Tape
PI-11 120-132" 120 to 132"Diameter Tape
PI-12 132-144" 132 to 144" Diameter Tape

In stock... tapes ranging from 38-200mm to 3300-3600mm diameter available for same day shipping.

Part No. Description    1095 Spring Steel
PI-M-0 28-200mm Diameter Tape
PI-M-1 100-300mm Diameter Tape
PI-M-1SP 50-600mm Diameter Tape
PI-M-2 300-600mm Diameter Tape
PI-M-2SP 300-900mm Diameter Tape
PI-M-3 600-900mm Diameter Tape
PI-M-3SP 600-1200mm Diameter Tape
PI-M-4 900-1200mm Diameter Tape
PI-M-5 1200-1500mm Diameter Tape
PI-M-6 1500-1800mm Diameter Tape
PI-M-7 1800-2100mm Diameter Tape
PI-M-8 2100-2400mm Diameter Tape
PI-M-9 2400-2700mm Diameter Tape
PI-M-10 2700-3000mm Diameter Tape
PI-M-11 3000-3300mm Diameter Tape
PI-M-12 3300-3600mm Diameter Tape
Standard clock steel will be supplied unless specified otherwise.
to order Stainless Steel add SS to end of part number


Extra Large Diameter Inch size tapes over 144" diameter ( special order )

       1095 Spring Steel
  (black numbers on silver)
Diameter Range O.D. Part#
144" - 156" P13
156" - 168" PI-14
168" - 180" PI-15
180" - 192" PI-16
192" - 204" PI-17
204" - 216" PI-18
216" - 228" PI-19
228" - 240" PI-20
240" - 252" PI-21
252" - 264" PI-22
264" - 276" PI-23
276" - 288" PI-24
288" - 300" PI-25
300" - 312" PI-26
312" - 324" PI-27
324" - 336" PI-28
336" - 348" PI-29
348" - 360" PI-30
360" - 372" PI-31
372" - 384" PI-32
384" - 396" PI-33
396" - 408" PI-34
408" - 420" PI-35
420" - 432" PI-36
432" - 444" PI-37
444" - 456" PI-38
456" - 468" PI-39
468" - 480" PI-40
480" - 492" PI-41
492" - 504" PI-42
504" - 516" PI-43
516" - 528" PI-44
528" - 540" PI-45
    Standard tapes are manufactured with a 1/4" wide Vernier Gage, a 1/2" wide Main Body and a 1/4" wide Gage Member
                                 Calibration Report traceable to N.I.S.T. furnished with each new tape at no additional charge.  
          Our calibration lab is compliant with ANSI/NCSL Z540-1-1994, ISO/IEC 17025, ISO 10012-1, MIL-STD 45662A and 10CFR21
    Tolerances for standard range tapes (12" of usable range) listed above
               Tape sizes between 144" - 216"     .003" tolerance
               Tape sizes between 216" - 288"     .005" tolerance
               Tape sizes between 288" - 360"     .006" tolerance

Extra Large Diameter Metric sizes tapes over 3600mm diameter ( special order )

Materials Available        1095 Spring Steel
  (black numbers on silver)
Diameter Range O.D. Part#
3600-3900mm PI-M-13
3900-4200mm PI-M-14
4200-4500mm PI-M-15
4500-4800mm PI-M-16
4800-5100mm PI-M-17
5100-5400mm PI-M-18
5400-5700mm PI-M-19
5700-6000mm PI-M-20
6000-6300mm PI-M-21
6300-6600mm PI-M-22
6600-6900mm PI-M-23
6900-7200mm PI-M-24
7200-7500mm PI-M-25
7500-7800mm PI-M-26
7800-8100mm PI-M-27
8100-8400mm PI-M-28
8400-8700mm PI-M-29
8700-9000mm PI-M-30
9000-9300mm PI-M-31
9300-9600mm PI-M-32
9600-9900mm PI-M-33
9900-10,200mm         PI-M-34
10,200-10,500mm PI-M-35
10,500-10,800mm PI-M-36
10,800-11,100mm PI-M-37
11,100-11,400mm PI-M-38
11,400-11,700mm PI-M-39
11,700-12,000mm PI-M-40
12,000-12,300mm PI-M-41
12,300-12,600mm PI-M-42
12,600-12,900mm PI-M-43
12,900-13,200mm PI-M-44
13,200-13,500mm PI-M-45
    Standard tapes are manufactured with a 6.35mm wide Vernier Gage, a 12.7mm wide Main Body and a 6.35mm wide Gage Member
                                  Calibration Report traceable to N.I.S.T. furnished with each new tape at no additional charge.  
          Our calibration lab is compliant with ANSI/NCSL Z540-1-1994, ISO/IEC 17025, ISO 10012-1, MIL-STD 45662A and 10CFR21
  Tolerances for standard range tapes (300mm of usable range) listed above
          Tape sizes between 3600-5400mm     .09mm tolerance
          Tape sizes between 5400-7200mm     .14mm tolerance
          Tape sizes between 7200-9000mm     .18mm tolerance


To Read Outside Diameter Tapes

How to use the tape
vernier scale
Standard width is 1/4" gage member. 1/8, 3/8 or 1/2" widths also available - extra charge per tape. Vernier scale divides each graduation on tape body into 25 parts or .001 of an inch
In the illustration the divisions to the left of the Vernier zero are 20 inches plus 1 division, or 20.025. The 15th line on the Vernier coincides with a line on the Gage Member. This is added to the 20.025, making a total diameter reading of 20.040, which is the true diameter reading as measured on the outside circumference. When reading the tape, apply a snug pull of 5 lbs. tension, first making sure the tape and part have been properly cleaned. When using a standard O.D. tape on an I.D. surface, add double the tape thickness to the reading to arrive at the I.D. of the part (0 lbs. tension). It is suggested that direct I.D. tapes be used for Inside Diameter readings.
Instructions on how to measure with Pi Tape® Inch Outside Diameter tapes on YouTube
vernier scale
Standard width is 6.35 mm gage member. 4.76, 9.53 or 12.70 mm widths also available - extra charge per tape

Each line on the Gage Member of the tape represents .5mm of Diameter, while each line on the Vernier represents .01mm. The zero on the Vernier is past the 661.5 line on the Gage Member of the tape. Now find the line on the Vernier which corresponds exactly with the line above. The example shows it to be the 23 line which equals .23mm. This added to the 661.5 reading gives an outside diameter of 661.73mm.
When reading the OD tape, apply a snug pull of 2.25kg. tension, first making sure the tape and part have been properly cleaned.
Inside diameters can be read in the same manner by adding double the tape thickness to the reading using the standard outside diameter tape ( 0kg tension). Standard tapes are .25mm thick; thus .50mm would be added to the reading. It is suggested that direct I.D. tapes be used for Inside Diameter readings.

As a suggestion for checking very large diameters-pieces of masking tape may be used to hold the tape in proper parallel position.

 Instructions on how to measure with Pi Tape® Metric Outside Diameter tapes on YouTube


When not in use, wipe clean and apply a light rust preventive oil. Store in tape container.

No periodic adjustments are needed.

Make sure the tape has not been stepped on or kinked, which may destroy the accuracy.


Specialty Items

link to Digital pi tape page

link to Special pi tape page

Precision O-Ring Inside Diameter tapes

are specifically designed to achieve quick, accurate inside diameter measurements of O-Rings and other soft-walled parts.

Trademarks are the properties of their respective owner(s).

Servicing the Canadian provinces and territories of
Newfoundland, NF, NL, Nova Scotia, NS, New Brunswick, NB, Prince Edward Island, PEI, PE, Quebec, PQ, QC, Ontario, ON, Manitoba, MB, Saskatchewan, SK, Alberta, AB, British Columbia, BC, Northwest Territories, NT, Nunavut, NU, Yukon, YT

Servicing Canadian cities,
Toronto, Mississauga, Scarborough, Laval , Montreal, Montréal, Vancouver, Ottawa, Gatineau, Calgary, Edmonton, Québec City, Winnipeg, Hamilton, Kitchener, Cambridge, Waterloo, London, St. Catharines , Niagara, Halifax, Oshawa, Victoria, Windsor, Saskatoon, Regina, Sherbrooke, St. John's, Barrie, Kelowna, Abbotsford, Mission, Sudbury Kingston, Saguenay, Trois-Rivieres, Trois Rivieres, Trois-Rivières, Guelph, Moncton, Brantford, Saint John, Thunder Bay, Peterborough, Ajax, Aurora, Brampton, Brock, Burlington, Caledon, Clarington, Durham Region, Oshawa, Pickering, Whitby, Halton Hills, Milton, Oakville, Mississauga, New market, Richmond Hill, Vaughn, Orangeville

Servicing US cities,
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