There are four separate online calculators available.
Number 1: Simple Heat Inputs, and gas rate app. Just like the ones on the app store.
Number 2: 🆕 2026 Purging and Leakage Rate Calculator. This will be mandatory in October 2026.
Number 3: Domestic Pipe Sizing Calculator for Natural Gas, LPG, Butane in Copper, Steel or PE Pipe