SDR (Standard Dimension Ratio) is the single most important number for specifying HDPE pipe wall thickness and pressure capacity. SDR = Outside Diameter ÷ Minimum Wall Thickness. A lower SDR number means a thicker wall and a higher pressure rating.
The Golden Rule
Lower SDR = Thicker Wall = Higher Pressure. SDR 41 is the thinnest wall (lowest pressure). SDR 6 is the thickest wall (highest pressure).
Complete SDR to PN Mapping — IS 4984:2016
This is the master reference table. The pressure rating (PN) depends on both SDR and material grade. Data sourced from IS 4984:2016 and the BIS Product Manual PM/IS 4984/2/June 2022 Annex A.
| SDR | PN (PE 63) | PN (PE 80) | PN (PE 100) | Typical Application |
|---|---|---|---|---|
| SDR 41 | PN 2 | PN 2.5 | — | Very low pressure gravity flow |
| SDR 33 | PN 2.5 | PN 3.2 | PN 4 | Low pressure distribution |
| SDR 26 | PN 3.2 | PN 4 | PN 5 | Rural water supply gravity systems |
| SDR 21 | PN 4 | PN 5 | PN 6 | Light pressure irrigation, sprinkler laterals |
| SDR 17 | PN 5 | PN 6 | PN 8 | Standard agricultural mains, sprinkler mainlines |
| SDR 13.6 | PN 6 | PN 8 | PN 10 | Town water supply, medium pressure |
| SDR 11 | PN 8 | PN 10 | PN 12.5 | High pressure water supply, borewell |
| SDR 9 | PN 10 | PN 12.5 | PN 16 | Municipal and industrial supply |
| SDR 7.4 | PN 12.5 | PN 16 | PN 20 | High pressure industrial |
| SDR 6 | — | PN 20 | PN 20 | Very high pressure (PE 80/100 only) |
Wall Thickness by SDR (110mm OD pipe)
Lower SDR = thicker wall = higher pressure capacity. Green bars are the strongest.
Relative Wall Thickness at a Glance
Each ring represents the pipe wall relative to the outer diameter. Thicker ring = more material = higher pressure.
Wall Thickness by Size — PE100 SDR 11 (Most Common)
| OD (mm) | Wall Thickness (mm) | SDR | Pressure (PE 100) | Weight (kg/m) |
|---|---|---|---|---|
| 20 | 2.0 | 11 | PN 12.5 | 0.12 |
| 25 | 2.3 | 11 | PN 12.5 | 0.17 |
| 32 | 2.9 | 11 | PN 12.5 | 0.28 |
| 40 | 3.7 | 11 | PN 12.5 | 0.44 |
| 50 | 4.6 | 11 | PN 12.5 | 0.68 |
| 63 | 5.8 | 11 | PN 12.5 | 1.08 |
| 75 | 6.8 | 11 | PN 12.5 | 1.46 |
| 90 | 8.2 | 11 | PN 12.5 | 2.12 |
| 110 | 10.0 | 11 | PN 12.5 | 3.14 |
| 125 | 11.4 | 11 | PN 12.5 | 4.08 |
| 140 | 12.7 | 11 | PN 12.5 | 5.08 |
| 160 | 14.6 | 11 | PN 12.5 | 6.67 |
| 200 | 18.2 | 11 | PN 12.5 | 10.4 |
| 250 | 22.7 | 11 | PN 12.5 | 16.2 |
| 315 | 28.6 | 11 | PN 12.5 | 25.7 |
| 400 | 36.3 | 11 | PN 12.5 | 41.4 |
| 500 | 45.4 | 11 | PN 12.5 | 64.7 |
| 630 | 57.2 | 11 | PN 12.5 | 102.6 |
How to Calculate SDR
SDR = Outside Diameter (OD) ÷ Minimum Wall Thickness. For example: A 110mm OD pipe with 10mm wall thickness has SDR = 110 ÷ 10 = SDR 11.
Wall Thickness Comparison — 110mm OD Pipe at Different SDRs
| SDR | Wall Thickness | PN (PE 80) | PN (PE 100) | Weight (kg/m) |
|---|---|---|---|---|
| SDR 26 | 4.2 mm | PN 4 | PN 5 | 1.39 |
| SDR 21 | 5.3 mm | PN 5 | PN 6 | 1.74 |
| SDR 17 | 6.6 mm | PN 6 | PN 8 | 2.14 |
| SDR 13.6 | 8.1 mm | PN 8 | PN 10 | 2.59 |
| SDR 11 | 10.0 mm | PN 10 | PN 12.5 | 3.14 |
| SDR 9 | 12.3 mm | PN 12.5 | PN 16 | 3.78 |
| SDR 7.4 | 14.9 mm | PN 16 | PN 20 | 4.44 |
BIS Size Groups (IS 4984:2016)
The BIS Product Manual PM/IS 4984/2/June 2022 categorises pipe sizes into 5 groups for certification purposes:
| Group | DN Range (mm) | Typical Form |
|---|---|---|
| Group I | 16 to 180 | Coils (50m, 100m) or straight lengths |
| Group II | 200 to 500 | Straight lengths (6m, 12m) |
| Group III | 560 to 1000 | Straight lengths (6m, 12m) |
| Group IV | 1200 to 2000 | Straight lengths (custom) |
| Group V | 2250 & 2500 | Straight lengths (custom order) |
Group V (DN 2250 and DN 2500) was added in the June 2022 revision of the BIS Product Manual. The January 2019 edition only covered sizes up to DN 2000mm across 4 groups.
Frequently Asked Questions
What does SDR mean on HDPE pipe?
SDR stands for Standard Dimension Ratio. It is the ratio of pipe outside diameter (OD) to minimum wall thickness. SDR = OD ÷ Wall Thickness. A lower SDR means thicker walls and higher pressure capacity.
What is the most common SDR for water supply?
SDR 11 is the most commonly specified SDR for municipal water supply (PN 10 for PE80, PN 12.5 for PE100). For agricultural sprinkler mainlines, SDR 17 (PN 6 for PE80) is standard.
How many SDR classes are there in IS 4984?
IS 4984:2016 defines 10 SDR classes: SDR 41, 33, 26, 21, 17, 13.6, 11, 9, 7.4, and 6.
Tools & Related Resources
Confused by a term? Look it up
FREE TOOLGet a PN & SDR recommendation
TECHNICAL GUIDEWhat is HDPE? Material, Pipe Grades, Standards & Uses
CHART & REFERENCEHDPE Pipe PN Pressure Rating Chart — IS 4984:2016
TECHNICAL GUIDEPE63 vs PE80 vs PE100: Complete Material Grade Comparison
TECHNICAL GUIDEHDPE Pipe Manufacturer in India
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