PED/PESR calculator
Find the conformity assessment category of a vessel, a pipe or a steam generator from its maximum allowable pressure, volume or nominal size, and the fluid.
Inputs
The working
- Maximum allowable pressure PS
as typed, bar gauge8 bar - Volume V
as typed100 L - PS x V
PS x V800 bar.L
For guidance only. Verify against the code edition in force and your own design basis.
Annex II, Table 2: Vessels, gases and vapours, fluid group 2
Directive 2014/68/EU, Annex II, Table 2 | UK Pressure Equipment (Safety) Regulations 2016, Schedule 1B, paragraph 4, Table 2
Selected by Directive Article 4(1)(a)(i) | UK Regulations regulation 6(a)(i)
- scope line (0.5 bar)
- category limit, named by its value
Chart used: Annex II table 2 (Vessels: gases, liquefied gases, gases dissolved under pressure, vapours, and liquids whose vapour pressure at the maximum allowable temperature is more than 0.5 bar above atmospheric pressure (1013 mbar), fluid group 2). PS in bar gauge against volume V in litres, both axes logarithmic.
Point plotted: PS 8 bar, V 100 L; PS x V 800 bar.L. Category: II.
Table 2: category II, within the upper limits of category II: PS x V not above 1000 bar.L and PS not above 1000 bar; above the category I limit (PS x V above 200 bar.L).
Lines drawn from the calculator's limit data, verified against the UK Pressure Equipment (Safety) Regulations 2016, Schedule 1B diagrams on 2026-10-07.
This PED/PESR calculator gives the category (SEP, or I to IV) of a pressure vessel, pipe or steam generator under Directive 2014/68/EU and the UK Pressure Equipment (Safety) Regulations 2016. Free, no sign-up.
The rule
- Equipment type, fluid state and fluid group pick one of nine tables (1 to 4 vessels, 5 steam generators, 6 to 9 piping).
- PS, and V or DN, and PS x V or PS x DN, are compared with that table's lines. A value exactly on a line takes the lower category.
- Below the scope lines: SEP. PS of 0.5 bar gauge or less: outside the Directive. Table 7 piping in category II with TS above 350 degC: category III.
Worked examples
Limits
Common questions
What is the PED category of pressure equipment and how is it decided?
The category, I to IV, sets how much third-party involvement the conformity assessment needs, with category I the lowest. It is read from the Annex II tables using the equipment type, fluid state and group, pressure PS, and volume V or nominal size DN. Below the scope lines the equipment is SEP and has no category.
What is the difference between PED and PESR?
The PED is the Pressure Equipment Directive, 2014/68/EU. PESR is short for the Pressure Equipment (Safety) Regulations 2016, the law in Great Britain that carries the same tables, so the category is the same under either.
What is sound engineering practice (SEP) under the PED?
SEP is the result for equipment at or below the scope lines of Article 4. It must be designed and made to sound engineering practice, but it has no category and is not CE marked under the Directive.
Does the PED/PESR calculator replace a notified body or approved body?
No. It is a guide to help you check your own classification. It does not replace the manufacturer's classification or the assessment of a notified body (or, in Great Britain, an approved body), so ask them if a result is close to a line.
Unit conversions
Reference values for the units this tool works in. Rounded for reading; the calculator itself works to full precision.
Pressure and stress
| MPa | bar | psi | ksi |
|---|---|---|---|
| 0.1 | 1 | 14.5 | 0.0145 |
| 0.5 | 5 | 72.52 | 0.0725 |
| 1 | 10 | 145 | 0.145 |
| 2 | 20 | 290.1 | 0.2901 |
| 5 | 50 | 725.2 | 0.7252 |
| 10 | 100 | 1,450 | 1.45 |
| 20 | 200 | 2,901 | 2.901 |
| 50 | 500 | 7,252 | 7.252 |
| 100 | 1,000 | 14,504 | 14.5 |
| 138 | 1,380 | 20,015 | 20.02 |
| 200 | 2,000 | 29,008 | 29.01 |
| 250 | 2,500 | 36,259 | 36.26 |
1 MPa = 10 bar = 145.04 psi. 1 ksi = 6.895 MPa.
Volume
| L | m³ | US gal | ft³ |
|---|---|---|---|
| 10 | 0.01 | 2.642 | 0.3531 |
| 50 | 0.05 | 13.21 | 1.766 |
| 100 | 0.1 | 26.42 | 3.531 |
| 250 | 0.25 | 66.04 | 8.829 |
| 500 | 0.5 | 132.1 | 17.66 |
| 1,000 | 1 | 264.2 | 35.31 |
| 2,000 | 2 | 528.3 | 70.63 |
1 m³ = 1000 L = 264.17 US gal.
Nominal size
| DN | NPS |
|---|---|
| 15 | 1/2" |
| 25 | 1" |
| 40 | 1-1/2" |
| 50 | 2" |
| 80 | 3" |
| 100 | 4" |
| 150 | 6" |
| 200 | 8" |
| 250 | 10" |
| 300 | 12" |
Nominal pipe sizes (DN and NPS).
Temperature
| °C | °F |
|---|---|
| 20 | 68 |
| 100 | 212 |
| 150 | 302 |
| 200 | 392 |
| 250 | 482 |
| 300 | 572 |
| 400 | 752 |
| 500 | 932 |
| 600 | 1,112 |
°F = °C x 9/5 + 32.
The category is worked from the pressure equipment charts and the scope limits. It is a first step: the manufacturer decides the final classification, and a notified body or approved body may be involved depending on the category and module.