Duct sizing calculator.
A free tool for UK ventilation and MVHR installers. Enter your design airflow and target velocity, get the standard spiral duct size in one step. Built by people who have actually installed ductwork, not just websites.
Exact fit is 206 mm, so the next standard spiral size up is 224 mm. Airflow then runs at 2.54 m/s in that duct.
Guidance only, based on A = Q / v. Real designs must account for fittings, pressure loss, noise, manufacturer data and current Building Regulations (Approved Document F). Not a substitute for a competent ventilation designer.
Most ventilation problems are baked in before anyone checks.
Undersize a duct and you get noise, poor airflow and a system that fails commissioning once everything is boxed in and plastered over. By then it is expensive, or impossible, to fix. The industry norm is to check only at the very end, with commissioning. That is too late.
Getting the basics right at design and first fix, sizing, routing, connections, is where the money and reputation are won or lost.
We're building VentTrace.
A staged ventilation QA system: checks tied to the drawings, photo and airflow evidence captured at each stage, deviations flagged before they are hidden, a documented trail for the developer or building control. Not to replace commissioning, to de-risk it.
- Catch defects at first fix, not at handover
- Evidence that matches Part F and the golden thread
- Less rework, fewer delays, protected reputation
Run a ventilation firm? Your website should speak the trade too.
We build sites and AI for ventilation and MVHR contractors, by people who know the work.