Pi Tape® Precision Diameter Measuring Tapes
Wrap it around a pipe, shaft, roller or vessel and read the diameter directly, to 0.001 inch. Outside and inside diameter, inch and metric, spring steel and stainless. Every model links straight to our online store, and each is built to your order by Pi Tape, typically shipping in 2–4 weeks.
Reads diameter
The scale is pre-divided by pi, so there is no calculation.
±0.001 inch
Pi Tape's stated precision, depending on range, with a vernier scale.
Calibrated
Each tape ships with a calibration report traceable through NIST.
0.5 in. to 144 in.
Standard OD range, and 15 to 3,600 mm metric; larger on request.
How a Pi Tape works
A standard tape measures circumference; dividing by pi to get the diameter adds rounding error. A Pi Tape's graduations already account for pi, so the reading where the tape overlaps is the diameter. A vernier scale reads the fine figure: 0.001 inch on inch tapes and 0.01 mm on metric tapes. That makes it faster than calipers, and it works on large diameters that calipers and micrometers cannot reach.
Used on pipe and piping, shafts and rollers, tanks, drums and pressure vessels, and machined parts, in industries from aerospace and oil and gas to mining, manufacturing and water infrastructure.
Choosing a Pi Tape
Pick the type (outside or inside), the measuring system, the blade, and the model whose range covers your diameter.
Outside diameter (OD)
- Inch 0.5 to 144 in.
- Metric 15 to 3,600 mm
For pipe, shafts, rollers, drums and vessels.
Inside diameter (ID)
- Inch 0.75 to 60 in.
- Metric 28 to 1,500 mm
For bores, rings and pipe interiors where an outside wrap is not possible. Larger diameters are OD only.
1095 spring steel
- Best for Non-corrosive conditions
- Model suffix None, e.g. P1
Pi Tape's standard, general-purpose blade for shop and field use.
716 stainless steel
- Best for Wet, washdown, marine, food, chemical
- Model suffix SS, e.g. P1SS
Choose stainless if the tape will see moisture over its life.
Easy-to-Read blue
- Best for Dim light, large parts
- Model suffix EZ, e.g. P1EZ
Higher-contrast graduations for faster reading. Offered on every standard range.
Extended range
- Examples P1SP 2 to 24 in.; P2SP 12 to 36 in.
- ID versions Add ID, e.g. P1SPID
One tape covering a wider span than a standard model, handy when part sizes vary.
Pi Tape model charts
Find the row that covers your diameter and click the model to open it in our store. Every standard size comes in all three finishes. 162 models are linked.
Outside diameter, inch
Swipe the table sideways to see every column →
| Diameter range | 1095 Spring Steel | 716 Stainless Steel | Blue Easy-to-Read |
|---|---|---|---|
| 0.5 – 2 in. | P000 | P000SS | P000EZ |
| 0.75 – 9 in. | P02 | P02SS | P02EZ |
| 2 – 12 in. | P1 | P1SS | P1EZ |
| 2 – 24 in. | P1SP | P1SPSS | P1SPEZ |
| 12 – 24 in. | P2 | P2SS | P2EZ |
| 12 – 36 in. | P2SP | P2SPSS | P2SPEZ |
| 24 – 36 in. | P3 | P3SS | P3EZ |
| 24 – 48 in. | P3SP | P3SPSS | P3SPEZ |
| 36 – 48 in. | P4 | P4SS | P4EZ |
| 48 – 60 in. | P5 | P5SS | P5EZ |
| 60 – 72 in. | P6 | P6SS | P6EZ |
| 72 – 84 in. | P7 | P7SS | P7EZ |
| 84 – 96 in. | P8 | P8SS | P8EZ |
| 96 – 108 in. | P9 | P9SS | P9EZ |
| 108 – 120 in. | P10 | P10SS | P10EZ |
| 120 – 132 in. | P11 | P11SS | P11EZ |
| 132 – 144 in. | P12 | P12SS | P12EZ |
Extended-range SP models are listed in size order (P1SP falls between P1 and P2).
Outside diameter, metric
Swipe the table sideways to see every column →
| Diameter range | 1095 Spring Steel | 716 Stainless Steel | Blue Easy-to-Read |
|---|---|---|---|
| 15 – 50 mm | PM000 | PM000SS | PM000EZ |
| 28 – 300 mm | PM02 | PM02SS | PM02EZ |
| 50 – 300 mm | PM03 | PM03SS | PM03EZ |
| 100 – 300 mm | PM1 | PM1SS | PM1EZ |
| 50 – 600 mm | PM1SP | PM1SPSS | PM1SPEZ |
| 300 – 600 mm | PM2 | PM2SS | PM2EZ |
| 300 – 900 mm | PM2SP | PM2SPSS | PM2SPEZ |
| 600 – 900 mm | PM3 | PM3SS | PM3EZ |
| 600 – 1200 mm | PM3SP | PM3SPSS | PM3SPEZ |
| 900 – 1200 mm | PM4 | PM4SS | PM4EZ |
| 1200 – 1500 mm | PM5 | PM5SS | PM5EZ |
| 1500 – 1800 mm | PM6 | PM6SS | PM6EZ |
| 1800 – 2100 mm | PM7 | PM7SS | PM7EZ |
| 2100 – 2400 mm | PM8 | PM8SS | PM8EZ |
| 2400 – 2700 mm | PM9 | PM9SS | PM9EZ |
| 2700 – 3000 mm | PM10 | PM10SS | PM10EZ |
| 3000 – 3300 mm | PM11 | PM11SS | PM11EZ |
| 3300 – 3600 mm | PM12 | PM12SS | PM12EZ |
PM02 (28 to 300 mm) and PM03 (50 to 300 mm) come before PM1; SP models are listed in size order.
Inside diameter, inch
Swipe the table sideways to see every column →
| Diameter range | 1095 Spring Steel | 716 Stainless Steel | Blue Easy-to-Read |
|---|---|---|---|
| 0.75 – 9 in. | P02ID | P02SSID | P02EZID |
| 2 – 12 in. | P1ID | P1SSID | P1EZID |
| 2 – 24 in. | P1SPID | P1SPSSID | P1SPEZID |
| 12 – 24 in. | P2ID | P2SSID | P2EZID |
| 12 – 36 in. | P2SPID | P2SPSSID | P2SPEZID |
| 24 – 36 in. | P3ID | P3SSID | P3EZID |
| 24 – 48 in. | P3SPID | P3SPSSID | P3SPEZID |
| 36 – 48 in. | P4ID | P4SSID | P4EZID |
| 48 – 60 in. | P5ID | P5SSID | P5EZID |
Inside diameter, metric
Swipe the table sideways to see every column →
| Diameter range | 1095 Spring Steel | 716 Stainless Steel | Blue Easy-to-Read |
|---|---|---|---|
| 28 – 300 mm | PM02ID | PM02SSID | PM02EZID |
| 50 – 300 mm | PM03ID | PM03SSID | PM03EZID |
| 100 – 300 mm | PM1ID | PM1SSID | PM1EZID |
| 50 – 600 mm | PM1SPID | PM1SPSSID | PM1SPEZID |
| 300 – 600 mm | PM2ID | PM2SSID | PM2EZID |
| 300 – 900 mm | PM2SPID | PM2SPSSID | PM2SPEZID |
| 600 – 900 mm | PM3ID | PM3SSID | PM3EZID |
| 600 – 1200 mm | PM3SPID | PM3SPSSID | PM3SPEZID |
| 900 – 1200 mm | PM4ID | PM4SSID | PM4EZID |
| 1200 – 1500 mm | PM5ID | PM5SSID | PM5EZID |
Inside-diameter tapes are made in the sizes shown; larger diameters are outside-diameter only.
Using and caring for a Pi Tape
Wrap it square
Clean the part and the tape and keep the tape square to the part's axis. On large parts, masking tape can hold it in position.
Use the right tension
Pi Tape specifies 5 pounds for inch OD tapes and 2.25 kg for metric OD tapes.
Read the vernier
Take the main-scale value at the vernier zero, then add the vernier line that lines up exactly.
Care and recertification
Wipe and lightly oil after use, store dry, and do not kink it. Pi Tape can recertify tapes with a new calibration certificate.
Pi Tapes are made by Pi Tape Texas, LLC in Tyler, Texas, which states it has made precision measuring tapes since 1944.
Pi Tape FAQ
Is Jealco an authorized Pi Tape distributor?
Yes. Jealco International is an authorized Pi Tape distributor, listed in Pi Tape's worldwide distributor network. The Pi Tape line, outside and inside diameter, inch and metric, spring steel and stainless, can be ordered through our online store, and we can source custom and extended ranges from the manufacturer.
How is a Pi Tape different from a regular tape measure?
A regular tape measures circumference, and dividing by pi to get the diameter adds rounding error. A Pi Tape's scale is already divided by pi, so when it is wrapped around a cylinder it reads the diameter directly, with a vernier for fine readings.
How accurate is a Pi Tape?
Pi Tape states precision to plus or minus 0.001 inch (0.03 mm), depending on range. The vernier reads to 0.001 inch on inch tapes and 0.01 mm on metric tapes. Every tape comes with a calibration report traceable through NIST.
How do I use a Pi Tape correctly?
Clean the tape and the part, wrap the tape square to the axis of the part, and apply the tension Pi Tape specifies: 5 pounds for inch outside-diameter tapes, 2.25 kg for metric. Read the main scale at the vernier zero, then add the vernier line that aligns exactly. On large parts, masking tape can hold the tape in position.
Imperial or metric: which do I need?
Match your drawings. Inch tapes read in inches and thousandths; metric tapes read in millimeters. The scales are different, so you need a separate tape for each system.
What diameters can Pi Tapes measure?
Standard outside-diameter tapes run from 0.5 inch up to 144 inches, and metric tapes up to 3,600 mm, with each model covering its own range. Inside-diameter tapes run up to 60 inches (1,500 mm). Larger and special tapes are made on request; send us the minimum and maximum diameter.
Spring steel or stainless steel?
Both read the same. 1095 spring steel is Pi Tape's standard for non-corrosive conditions. 716 stainless steel suits corrosive, wet, washdown, marine and food environments. Every standard range also comes in an Easy-to-Read blue finish for higher contrast.
Can my Pi Tape be recalibrated?
Yes. Pi Tape offers a recertification service with a new calibration certificate; standard turnaround is two to five weeks. Contact us and we will arrange it.
How long does a Pi Tape take to ship?
Pi Tapes are built to your order by Pi Tape and typically ship in 2 to 4 weeks. Order online, or send us the model, range and measurement system and we will confirm the lead time and price.
PI TAPE® and its logo are trademarks of Pi Tape® Texas, LLC, registered in the USA and in 45 other countries. Images used by permission of the owner. Specifications are from Pi Tape's published information.
Not sure which Pi Tape fits?
Send us the smallest and largest diameters you measure, inside or outside, and inch or metric. We will recommend the model and confirm lead time.