Calculated result
240CFM
Planning airflow
Formula
HVAC-CFM-001CFM = length × width × height × ACH ÷ 60
2400 ft³
Room volume
6 ACH
Air changes per hour
113.27 L/s
L/s
HVAC calculator
CFM calculator
CFM calculator publishes formula HVAC-CFM-001 version 1.0.0.
By Feroz Shiekh · Formula HVAC-CFM-001 v1.0.0 · Internal QA complete · Planning only — not a supplier quote
Formula
HVAC-CFM-001v1.0.0Project inputs
Enter field measurements. Imperial lengths take feet and inches. Unit conversion happens before the reviewed formula is applied.
All values can be refined when you edit the estimate. This tool does not replace field verification or local requirements.
CFM calculator publishes formula HVAC-CFM-001 version 1.0.0. CFM calculator for planning airflow from room volume and air changes per hour. Waste, rounding and the rate you type stay on the sheet so a quote letter can still explain the number. Add the line to an estimate. Planning takeoff only — not a code approval and not a live supplier price.
- Formula HVAC-CFM-001 version 1.0.0 is the arithmetic on this cfm calculator page and on the quote letter.
- HVAC takeoff: Planning airflow from room volume and air changes per hour. Not a duct design or Manual D. Waste and purchase rounding stay visible inputs, not hidden constants.
- Add the cfm calculator result to an estimate, then send a quote letter — an old letter still explains itself.
- You type the unit rate. Construclytic does not fetch supplier prices for this hvac tool.
- Planning takeoff only. The cfm calculator is not a code approval, mix design, or PE stamp.
Transparent cost view
Geometry pages start at zero. Add a planning rate only if you are pricing a related line. Pick a currency — badges, inputs, and totals follow.
This page is geometry, not a material takeoff. Leave rates at zero unless you are pricing a related line. Construclytic does not fetch supplier prices.
How this calculator works
A transparent cfm takeoff.
Feroz ShiekhWritten by Feroz Shiekh · founder
Planning CFM is room volume times air changes per hour, divided by 60. Not a duct design or Manual D.
HVAC-CFM-001 is planning airflow: room volume × air changes per hour ÷ 60. A 20 × 15 × 8 ft room at 6 ACH is 240 CFM. Not Manual D, not a duct size, not register throw and not a ventilation-code path.
Worked example. Example: a 20 × 15 × 8 ft room at 6 air changes per hour returns 240 CFM.
- 1. Measure the room that will be supplied, not the whole floor unless you mean that.
- 2. ACH is a planning input. Occupied rooms, shops and toilets do not share a number.
- 3. Duct size, static pressure and the fan curve stay with the designer.
Field notes that change the number
- Measure the room that will be supplied, not the whole floor unless you mean that.
- ACH is a planning input. Occupied rooms, shops and toilets do not share a number.
- Duct size, static pressure and the fan curve stay with the designer.
Common mistakes
- Using 6 ACH as if it were a code number.
- Sizing ducts from this CFM alone.
- Treating this as a balanced-ventilation or Manual D design.
Need the broader workflow? Read the hvac planning guide.
How-to: How to plan a furnace BTU load
Questions
Questions about cfm
Is 6 ACH a code number?
It is a common occupied-room start, not a ventilation-code path.
Does this size ducts?
No. Manual D, friction rate and register throw are not on this page.
What is the formula ID?
This cfm calculator publishes formula HVAC-CFM-001, version 1.0.0. The ID stays on the result and on the estimate line.
Is this engineering advice?
No. The cfm calculator is a planning takeoff. Construclytic is not a registered engineering or contracting firm. Field checks, codes and product data still sit with you.
Does Construclytic fetch live supplier prices?
No. Costs on the cfm calculator use the rate you enter. Construclytic does not fetch live supplier prices.