Use this serpentine belt size chart to compare rib profiles, decode effective length, and separate reference belt height from actual product thickness. Start with the size codes below: 6PK1000 and 6K1000 are different belts. Their rib geometry matches, but their encoded lengths use different units. The same belts are also sold as Poly-V, Micro-V, or multi-ribbed belts. Sizing a classical or narrow V belt instead? Use the V-belt size chart and cross-reference.
| Generic size code | Rib count | Profile | Effective length, Le |
|---|---|---|---|
| 6PK1000 | 6 | PK | 1000 mm |
| 6K1000 | 6 | K | 100.0 inches = 2540 mm |
| 8PK1600 | 8 | PK | 1600 mm |
These are public dimensional-code examples, not a stock list or a vehicle fitment catalogue. A matching code identifies dimensions to check; it does not establish material, duty rating, or approval for a particular drive.
Table of Contents
- How to read a serpentine belt size code
- PK size decoder: ten codes, field by field
- Poly-V profile dimensions: PH, PJ, PK, PL and PM
- PK belt width by rib count
- Belt height: standard reference versus market thickness
- How to identify a belt when only the old sample remains
- Metric and imperial length conversion
- Which profile is used for automotive accessory drives?
- What to include in a LYBELT enquiry
- Frequently asked questions
How to read a serpentine belt size code
Read the marking as separate fields: rib count, profile, and effective length. In 6PK1000, the initial 6 means six ribs, PK identifies the profile, and 1000 means an effective length of 1000 mm. In 8PK1600, the belt has eight ribs, the same PK profile, and an effective length of 1600 mm.
The imperial K convention needs special attention. In 6K1000, the initial 6 still means six ribs, but the numerical suffix represents inches multiplied by ten. The suffix 1000 therefore means 100.0 inches, equivalent to 2540 mm. It does not mean 1000 mm.
Never replace 6PK1000 with 6K1000 on the strength of the shared digits. The latter is about two and a half times as long. Copy the complete marking, including the P where present, and ask the supplier to state the length unit explicitly.
For the coding conventions explained here, length means Effective Length (Le), not outside circumference. Keep that definition on drawings, enquiries, and purchase orders. A number without its unit and measurement basis is an incomplete specification.
PK size decoder: ten codes, field by field
A V-ribbed belt is designated by the number of belt ribs, the profile letters, and the effective length in millimeters. ISO 9982:1998 as published in India (IS 15151:2002) sets that order. On a PK code, the first number is the rib count, the letters are the profile, and the second number is effective length Le in millimeters. This chart decodes ten example codes with that rule. A rib count alone, or a length alone, does not complete the designation.
| Marking | Ribs | Profile | Effective length Le (mm) | Le (in) |
|---|---|---|---|---|
| 4PK890 | 4 | PK | 890 | 35.04 |
| 6PK1040 | 6 | PK | 1040 | 40.94 |
| 6PK1070 | 6 | PK | 1070 | 42.13 |
| 6PK1255 | 6 | PK | 1255 | 49.41 |
| 6PK1555 | 6 | PK | 1555 | 61.22 |
| 6PK2135 | 6 | PK | 2135 | 84.06 |
| 6PK2345 | 6 | PK | 2345 | 92.32 |
| 6PK2415 | 6 | PK | 2415 | 95.08 |
| 7PK1300 | 7 | PK | 1300 | 51.18 |
| 7PK1320 | 7 | PK | 1320 | 51.97 |
Designation order: ISO 9982:1998 as published in India (IS 15151:2002). Inch values are the millimeter values divided by 25.4.
Use the table to decode a marking, then check rib count, profile and length together. Brands round the metric number differently by a millimeter or two, according to a belt distributor’s guide to ribbed belt numbers. Confirm the specification before ordering.
Poly-V profile dimensions: PH, PJ, PK, PL and PM
The metric and imperial profile names below describe the same rib-pitch geometry. PK and K are not different cross sections simply because their letters differ. The dimensional problem arises when the length suffix is interpreted using the wrong unit convention.
| Metric profile | Imperial profile | Rib pitch | Groove angle | Minimum effective pulley diameter |
|---|---|---|---|---|
| PH | H | 1.60 ± 0.03 mm | 40° | 13 mm |
| PJ | J | 2.34 ± 0.03 mm | 40° | 20 mm |
| PK | K | 3.56 ± 0.05 mm | 40° | 45 mm |
| PL | L | 4.70 ± 0.05 mm | 40° | 75 mm |
| PM | M | 9.40 mm | 40° | 180 mm |
Rib pitch is the spacing between corresponding points on adjacent ribs. It is not total belt width. Groove angle is also a profile characteristic, not a belt-routing angle. The listed minimum effective pulley diameters are dimensional references for selection; they do not replace an application assessment of load, speed, tensioning, and belt construction.
PK belt width by rib count
Nominal belt width is b = n x Pb, where n is the number of ribs and Pb is the rib pitch. ISO 9982:1998 as published in India (IS 15151:2002) gives that formula and lists PK rib pitch Pb as 3.56 mm. A 6-rib PK belt is 6 x 3.56 = 21.36 mm nominal, computed from the formula. The table extends the same formula to 3 to 10 ribs.
| Ribs (n) | Nominal width b (mm) | b (in) |
|---|---|---|
| 3 | 10.68 | 0.42 |
| 4 | 14.24 | 0.56 |
| 5 | 17.80 | 0.70 |
| 6 | 21.36 | 0.84 |
| 7 | 24.92 | 0.98 |
| 8 | 28.48 | 1.12 |
| 9 | 32.04 | 1.26 |
| 10 | 35.60 | 1.40 |
b = n × Pb with PK rib pitch Pb = 3.56 mm (ISO 9982:1998 as published in India (IS 15151:2002)). Inch values are the millimeter values divided by 25.4.
These are nominal widths computed from the formula, not measured widths of finished belts, and not a list of belts that exist. ISO 9982:1998 as published in India (IS 15151:2002) shows rib pitch and belt height as reference dimensions only. Count the ribs on a sample rather than trusting a caliper reading on a worn belt. On a worn sample, check the signs of a bad serpentine belt separately from this width.
Belt height: standard reference versus market thickness
Do not turn a reference belt height into a mandatory finished-product thickness. ISO 9982 includes the note: “Belt rib pitch and belt height are shown as reference dimensions only.” The pitch values above retain the stated tolerances; the reference heights below must not be treated as manufacturing acceptance tolerances.
| Profile | ISO 9982 / DIN 7867 reference belt height | Common market thickness, manufacturer catalogues |
|---|---|---|
| PH | ≈3 mm | 2.5 mm |
| PJ | ≈4 mm | 3.3–3.8 mm |
| PK | ≈6 mm; automotive ISO 9981: 4–6 mm, also reference values | 4.6–5.0 mm |
| PL | ≈10 mm | 7.0–9.0 mm |
| PM | ≈17 mm | 12.0–14.5 mm |
An automotive PK belt is not automatically 6 mm thick. Its actual thickness must come from the manufacturer’s specification. Catalogue thickness and a standard’s reference height serve different purposes, so combining them into a single “correct thickness” column would mislead a buyer inspecting a sample.
The market figures describe commonly listed products, not permitted variation for every belt. Construction can differ while retaining the required rib geometry. For incoming inspection, obtain the product drawing, the defined thickness measurement method, and the agreed tolerance. A worn sample is useful evidence, but it cannot establish the original production tolerance.
How to identify a belt when only the old sample remains
Record the marking and rib count
With the drive safely isolated, inspect the removed belt under good lighting. Photograph every readable portion of the marking before cleaning it. Record partial characters as uncertain rather than guessing. Count the longitudinal ribs on the belt itself; if damage makes the count unclear, compare the sample with the pulley and the drive documentation.
Check the profile and condition
Use a suitable measuring tool to inspect rib spacing across several undamaged ribs, then compare it with the profile table. Measuring a span across several pitches can make an identification easier than relying on a worn rib edge. Record cracking, missing material, polishing, and uneven wear separately from your measurements.
Measure thickness at intact areas with light, consistent contact. Do not squeeze a flexible belt until the reading resembles a reference value. Treat thickness as supporting identification evidence, not the deciding factor between profiles.
Measure circumference without calling it Le
Use a flexible tape around the belt’s outside surface without deliberately stretching it. Record the result as measured outside circumference, together with the method and sample condition. If the loop is broken or badly distorted, label any length estimate accordingly. Do not silently substitute that estimate for a catalogue length.
The outside surface follows a different measurement path from effective length. Belt construction and the measurement setup matter, so there is no universal subtraction to apply to every profile. A tape reading needs a product-specific conversion or confirmation using the appropriate effective-length measurement procedure.
Confirm effective length before ordering
ISO 9982 defines a “Measuring fixture to determine effective length.” Ask the supplier to identify the sample using the applicable fixture and procedure, or supply a documented relationship between its stated circumference and Le. Send the marking photographs, rib count, profile observations, and circumference reading together. Then confirm the proposed belt against the equipment’s specified routing and tensioner requirements.
Metric and imperial length conversion
Decode the suffix before converting units. For the PK examples here, the suffix states millimetres directly. For the imperial K convention, divide the suffix by ten to obtain inches. Dropping or adding the letter P is not a conversion.
Use the relationship 100.0 inches = 2540 mm. Written as a calculation, Le in millimetres equals Le in inches multiplied by (2540 ÷ 100.0). For the reverse direction, multiply Le in millimetres by (100.0 ÷ 2540). Preserve the measurement basis: converting an outside circumference into another unit still leaves it an outside circumference.
Specify the required effective length explicitly when placing an order. A calculated conversion does not prove that a corresponding stocked belt exists, and rounding to a nearby catalogue length needs application approval.
Which profile is used for automotive accessory drives?
PK is a common automotive accessory-drive profile. Rib count depends on the drive layout and required capacity; profile alone does not select it. The six-rib and eight-rib codes in the opening chart illustrate how to read rib count, rather than defining a universal automotive fitment range.
Use the vehicle or equipment specification to establish the required count and length. Do not choose a narrower belt simply because it can sit in some of a pulley’s grooves. Confirm routing, pulley condition, alignment, and the specified tensioning arrangement when investigating a replacement. A dimensional match cannot explain or cure an underlying drive fault.
What to include in a LYBELT enquiry
Send the complete code, required quantity, application, and any available drawing. State rib count, profile, effective length and unit separately. If identification starts from a sample, attach the photographs and measurements described above, clearly separating observed dimensions from confirmed specifications.
Also identify operating conditions and any agreed material, inspection, or validation requirements. Ask for a product specification before approving supply. LYBELT was established in 1999 and offers OEM/ODM manufacturing; those services do not imply authorization by an equipment manufacturer.
Frequently asked questions
Are PK and K the same profile?
They identify the same rib-pitch geometry in the conventions described here. Their length notation differs, however. Confirm the complete code, unit, and effective length before comparing offers.
Can I substitute 6K1000 for 6PK1000?
No. 6PK1000 specifies 1000 mm effective length; 6K1000 specifies 100.0 inches, or 2540 mm. Matching rib count and similar-looking digits do not make these belts interchangeable.
Can an outside tape measurement identify the ordered length?
It helps narrow the search, but it is not a direct Le measurement. Label it as outside circumference and obtain the applicable conversion or fixture-based effective-length confirmation.
Does a PK belt below the reference height fail inspection?
Not on that observation alone. Standard reference height is not a finished-belt acceptance tolerance. Check actual thickness against the specified product drawing and inspection method.
Does matching size guarantee the same service life?
No. Size does not establish construction, material performance, power capacity, or durability. Evaluate the proposed belt against the operating conditions and agreed validation requirements.
What if the marking has worn away completely?
Provide the old sample, rib count, profile measurements, photographs, and equipment details. Keep uncertain readings labelled. Approve a replacement only after its specification and application fit have been confirmed.
How wide is a 6PK belt?
A 6PK belt has 6 ribs and a nominal width of 6 x 3.56 mm = 21.36 mm, about 0.84 in (ISO 9982:1998 as published in India (IS 15151:2002)).
What does 7PK1320 mean?
7PK1320 means 7 ribs, the PK profile and an effective length of 1320 mm, about 51.97 in. The order of those fields is set by the standard (ISO 9982:1998 as published in India (IS 15151:2002)).
Have a belt code or a worn belt and need it matched? LYBELT has built rubber power-transmission belts since 1999 under IATF 16949. Send the size code, rib count, and effective length to our engineering team. For background on why the same belt carries several names, see multi-groove belt naming explained.
About Longyi Rubber Products Factory
LYBELT is the brand of Longyao County Longyi Rubber Products Factory (General Partnership), based in Longyao County, Xingtai, Hebei, China, and making rubber belts since 1999. The factory holds IATF 16949 and ISO 9001 certification and works from 130+ rubber compounds.
The range covers automotive, industrial, agricultural, ATV/UTV and motorcycle belts. For OEM and ODM orders, belts are made to the customer’s part number, drawing or size, with private label and packaging. Email: luxin@lybelt.com.
Independent-manufacturer disclaimer
LYBELT is an independent manufacturer and is not affiliated with, authorized by, or endorsed by any third-party brand. The generic size codes on this page describe dimensional envelopes under public standards. Dimensional agreement does not establish identical construction, power rating, service life, or OEM approval. These charts support identification and specification discussions; suitability for a particular drive requires application-specific verification.