Why start with an online ductulator?
An online ductulator calculator mirrors the Manual D slide-rule workflow while layering in instant unit conversion, warning logic, and copy-and-share results. That means you can move from load calculations to documented duct schedules in minutes without flipping through tables. This guide shows how HVAC designers, estimators, and technicians can validate layouts using the Online Ductulator and the Trane TD1 digital wheel.
Step-by-step: master bedroom run
- Start with airflow. From your Manual J load, the master bedroom needs 280 CFM. Enter that into the duct sizing calculator while the toggle is set to Imperial.
- Select a velocity target. Bedrooms prefer 600–700 FPM to keep noise down, so punch in 650 FPM and leave friction blank.
- Review the output. The tool recommends an 8 in round duct (or 4 × 12 in rectangular) and shows the resulting 0.074 in. w.g./100 ft friction, which is inside Manual D guidance.
- Check the metric view. Flip to Metric to see the same run as 132 L/s at 3.3 m/s with 0.6 Pa/m. These dual numbers drop straight into international spec sheets.
- Document the decision. Copy the result card into your notes or RFI response so reviewers see both the inputs and the derived velocity/friction.
Need to force a rectangular duct between joists? Switch the calculator to rectangular mode, choose a 3:1 aspect ratio, and rerun. The Huebscher equivalent diameter formula keeps friction loss honest even when the duct is flattened.
Quick checklist for every run
- Stay between 600–900 FPM for supply branches; upsize trunks if they exceed 900 FPM.
- Hold friction under 0.10 in. w.g./100 ft (0.8 Pa/m) unless you’re working on a high-pressure system.
- Keep rectangular aspect ratios ≤4:1 to avoid extra turbulence; the calculator flags anything higher.
- Use the Round↔Rectangular tool to match diffusers or retrofit ducts without reworking the entire layout.
- Cross-check velocity outputs against the quick reference table on the homepage for a visual sanity check.
Next steps
Once each critical run is sized, open the Trane TD1 calculator to verify the sleeve alignment visually, then export the values into your scheduling software. Bookmark this guide and share it with crews who still rely solely on physical ductulators so everyone works from the same online workflow.