Free tool for Gas Safe registered installers

Size a Flexigas gas pipe run.

Add the appliances, the run length and the fittings. The calculator gives you the recommended Flexigas DN size, checks it against the BS 6891 pressure-drop budget, and shows the full sizing ladder. Built straight from the Flexigas Installation Manual. The answer updates as you type.

BS 6891:2015 BS EN 15266:2007 Kitemark KM 598726 Live result

The tool

Size the run.

Single run, meter to appliance. The result updates as you go. No Calculate button.

Free Flexigas sizing for Gas Safe engineers.

Tell us who you are and the calculator unlocks. It stays open for the rest of your visit.

We use your details to open the tool and to reply if you raise a Flexigas technical question. We rely on legitimate interest for that follow-up and you can object at any time. We do not share your details outside Flexiridge Limited. See our privacy policy.

Gas type

Natural gas sizes to the 1 mbar BS 6891 budget. Propane and butane use the 2.5 mbar BS 5482 budget.

Appliances on this run

Add every appliance the run feeds. Rates are the manual's typical gross figures in m³/h. Override from the appliance data plate when you have it.

Total load0 m³/h

Run length

Meter to the furthest appliance

Fittings on the run

Each fitting adds an equivalent length. Formed bends in the tube are far lower loss than elbow fittings.

Advanced Budget allocation

Pressure-drop budget 1.0 mbar

BS 6891 allows 1 mbar across the whole natural gas run from meter to appliance. Lower this only when this run shares the budget with other legs of a larger system. Multi-section sizing is coming in the next release.

Why this size? The full sizing ladder

BS 6891:2015 IGEM/UP/2 BS EN 15266:2007 Kitemark KM 598726

BS 6891:2015 and IGEM/UP/2. Based on the Flexigas Installation Manual UK.

For sizing guidance only. All gas installations must be designed, installed, and verified by a Gas Safe registered engineer in accordance with the Gas Safety (Installation and Use) Regulations 1998. Always refer to the current Flexigas Installation Manual.

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Project support

Sizing a tricky run?

Talk to the Flexigas technical team about routing, terminations, multi-appliance runs or commercial sizing, or find your nearest stockist.

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