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How to Measure Bearing Dimensions: 2026 Replacement Guide

How to Measure Bearing Dimensions: 2026 Replacement Guide

Standard bearing dimensions are measured in millimeters using a digital caliper in a strict format - Bore (inner diameter) x Outer Diameter (OD) x Width. A single millimeter of error can lead to ordering the wrong part, causing unnecessary machine downtime and higher total maintenance costs. When replacing a worn bearing from HI-TEC ASIA's extensive catalog of over 2,000 products, knowing the exact physical size ensures you select a quiet, reliable, and low-maintenance replacement. Whether you are a workshop mechanic or a factory procurement officer, understanding these dimensions is critical for keeping your equipment running smoothly. This guide explains how to read metric bore size codes, decode part numbers, and use a digital caliper to confidently identify your exact replacement bearing.

What is the standard bearing dimension format and how do you measure it?

Standard bearing dimensions are measured in millimeters using a digital caliper in a strict format - Bore (inner diameter) x Outer Diameter (OD) x Width[1][2][3][4]. Written technically as d x D x B, these three measurements define the physical envelope of standard rolling bearings[5][3][4]. If a bearing part number is faded, mechanics can measure the inner ring, outer ring, and width to find the exact HI-TEC ASIA replacement. Accurate measurement requires a digital caliper, a clean bearing, and proper technique. Dirt or old grease can introduce measurement errors of 0.05 mm or more, which may lead you to the wrong size category[2].

Here is how to accurately measure a bearing with a digital caliper:

  1. Zero the digital caliper: Close the jaws lightly and ensure the display reads zero before starting your measurements[6][7]. Always set the unit to millimeters[1][2][5].
  2. Measure the bore (inner diameter): Insert the small, upper inside jaws into the bearing's inner ring[2][6]. Open the jaws gently until they make firm contact, then rock the caliper slightly to find the maximum reading[2][8][9]. Take measurements at three different points to ensure perfect accuracy[2][8].
  3. Measure the outer diameter (OD): Place the bearing between the large, lower outside jaws[2][6][10]. Close the jaws gently against the outer ring, keeping them perfectly square to the surface to avoid angled readings[6][8][9].
  4. Measure the width (thickness): Stand the bearing on a flat, clean surface. Use the outside jaws to measure the distance across the two side faces, keeping the jaws perfectly perpendicular to the faces[2][6][7].

Once you have these three numbers, you can easily match them against the HI-TEC ASIA bearing catalog and replacement parts to secure a quiet, reliable replacement.

How do you read metric bearing bore size codes?

Metric bearing part numbers use specific bore size codes, where a code of 04 equals 20mm and 05 equals a 25mm inner diameter[11][12][5][13]. Understanding this standardized numbering system allows mechanics and procurement staff to instantly identify a bearing's inner diameter without even touching a caliper. For standard bearings with a bore size of 20 mm and above, the last two digits of the basic designation represent the bore code, which you multiply by five to get the inner diameter in millimeters[11][5][4][14].

For example, a standard 6205 series bearing will always measure exactly 25mm in bore, 52mm in outer diameter, and 15mm in width[15][16][17]. The "05" at the end of 6205 is the bore code, and 5 multiplied by 5 equals a 25 mm bore[15][16][17]. This standardized rule applies across all major metric bearing types, ensuring consistency for buyers.

Here is a quick reference table for decoding standard metric bore size codes, using the popular 6200 series as a practical example:

Bore Code Calculation Inner Diameter (Bore) Example Bearing Standard Dimensions (Bore x OD x Width)
04 04 x 5 20 mm[11][12] 6204 20 mm x 47 mm x 14 mm[16]
05 05 x 5 25 mm[11][12] 6205 25 mm x 52 mm x 15 mm[15][16][17]
06 06 x 5 30 mm[16] 6206 30 mm x 62 mm x 16 mm[16]
07 07 x 5 35 mm[16] 6207 35 mm x 72 mm x 17 mm[16]

Note that bore codes 00, 01, 02, and 03 are exceptions to the multiply-by-five rule. They correspond to 10 mm, 12 mm, 15 mm, and 17 mm bores respectively[11][12][5][18][14]. By cross-referencing your measured dimensions or bore codes with a metric ball bearing size chart and specifications, you can quickly select the correct HI-TEC or premium HI-TEC SILVER bearing for your machinery.

Frequently Asked Questions

How do I measure bearing dimensions with a digital caliper?

Clean the bearing thoroughly, zero your caliper, and set it to millimeters[1][2][5]. Use the upper inside jaws to measure the inner bore, the lower outside jaws to measure the outer diameter, and the outside jaws again to measure the width across the side faces[2][6][7].

What is the standard bearing dimension format?

Standard rolling bearings use a three-dimension format expressed as Bore (inner diameter) x Outer Diameter (OD) x Width, written in millimeters as d x D x B[1][2][3][4]. This format is the universal standard used in supplier catalogs.

How do I read metric bearing bore size codes?

For metric bearings with bores of 20 mm or larger, look at the last two digits of the part number. Multiply that two-digit bore code by five to find the inner diameter in millimeters[11][5][13][4]. For example, a code of 04 equals a 20 mm bore[11][12].

How do I find a replacement bearing if the part number is faded?

If the part number is illegible, use a digital caliper to carefully measure the bore, outer diameter, and width in millimeters. You can then match these three dimensions against a standard bearing size chart to identify the correct replacement series from HI-TEC ASIA.

References

  1. Ball Bearing Size Chart: 6000, 6200, 6300, 6800, and 6900 Series. https://iskbearing.com/news/knowledge/the-ball-bearing-size-chart (2026-06-17)
  2. How Do You Measure a Bearing? A Step-by-Step Guide. https://www.andebearing.com/blog/how-to-measure-a-bearing (2026-05-13)
  3. [PDF] Parameters for dimensions and structure of bearing designations. https://www.nsk.com/content/dam/nsk/eu/en_gb/documents/bearings-europe/P_TI-0111_EN.pdf (2026-07-08)
  4. [PDF] Rolling bearings | SKF. https://www.skf.com/binaries/pub12/Images/0901d196802809de-Rolling-bearings---17000_1-EN_tcm_12-121486.pdf (2025-03-11)
  5. [PDF] Technical Report - NSK Ltd.. https://www.nsk.com/content/dam/nsk/common/catalogs/ctrgPdf/bearings/e728.pdf (2025-01-27)
  6. How to Use Digital Calipers - System Scale. https://www.system-scale.com/how-to-use-digital-calipers (2025-07-02)
  7. Proper Use of Digital Calipers - Bantam Tools. https://support.bantamtools.com/hc/en-us/articles/115001656313-Proper-Use-of-Digital-Calipers (2025-06-20)
  8. Getting the Most out of Digital Calipers - The BYU Design Review. https://www.designreview.byu.edu/collections/getting-the-most-out-of-digital-calipers (2020-06-10)
  9. I wish i'd known this sooner, How to use calipers like a pro - YouTube. https://www.youtube.com/watch?v=7u0PIz7deu8 (2024-08-12)
  10. [PDF] Bearing Dimension Catalog | Timken. https://www.timken.com/wp-content/uploads/2016/11/7011_Bearing-Dimension-Catalog.pdf (2026-07-08)
  11. Basic bearing designation system | SKF. https://www.skf.com/us/products/rolling-bearings/principles-of-rolling-bearing-selection/general-bearing-knowledge/bearing-basics/basic-bearing-designation-system
  12. Basic Designation System of Rolling Bearings | Bore Code - YouTube. https://www.youtube.com/watch?v=3VR9k516kE8 (2025-08-09)
  13. Bearing data | Schaeffler medias. https://medias.schaeffler.us/en/knowledge-center/rolling-bearings/bearing-data (2026-06-29)
  14. Bearing number | Basic Bearing Knowledge - ジェイテクト. https://koyo.jtekt.co.jp/en/support/bearing-knowledge/6-3000.html (2026-07-04)
  15. 6205 - Deep Groove Ball Bearings -25x52x15mm - isk bearings. https://iskbearing.com/news/knowledge/6205-bearing-dimensions-more-about-25-x-52-x-15mm (2025-01-09)
  16. 6205 Deep groove ball bearing - BYWB Bearing. https://bywbbearing.com/6205-deep-groove-ball-bearing/ (2025-07-21)
  17. Deep Groove 6205 Ball Bearings 25mm X 52mm X 15mm. https://us.misumi-ec.com/blog/ball-bearings/deep-groove/6205-ball-bearings-25x52x15mm-z-zz-2rs/ (2019-02-22)
  18. [PDF] Roller and Ball Bearings Design Guide. https://www.nhbb.com/sites/nhbb/files/2020-05/nhbb-large-ball-and-roller-bearing-products-and-engineering-catalog-2010.pdf (2026-06-20)