Cooling Load Estimator
Estimate cooling load, equipment tonnage, ventilation impact, and safety margin.
Open ToolAirflow & CFM Calculator
A multi-method airflow calculator that compares air change, people-based ventilation, and cooling-ton based airflow methods.
What is an airflow and CFM calculator?
An airflow and CFM calculator compares common HVAC airflow methods so the governing requirement is easier to see. It calculates airflow from air changes per hour, people-based ventilation, and cooling tons, then applies a design margin to the largest relevant value. Engineers use it when ACH, occupancy, and cooling-load rules point to different airflow quantities and the design team needs a clear planning number. It helps with room ventilation checks, supply air estimates, exhaust comparison, diffuser planning, and early AHU or FCU coordination. The result is a planning airflow only. Final design still needs ventilation code compliance, thermal load calculation, pressure loss, air distribution, filtration, acoustic limits, equipment selection, and local authority requirements. For best results, keep the entered units consistent, load the sample first, then adjust one assumption at a time so the result can be reviewed and explained.
Inputs
Forms are empty on load. Use sample data to preview the workflow or enter your own project values.
Learn more
Formula logic, use cases, assumptions, and limits for this tool.
How this tool helps
Use this when different airflow methods give different answers. The recommended planning airflow is based on the governing method plus margin.
Assumptions and limits
This tool provides a planning-level result. It does not replace detailed engineering design, approved software, manufacturer data, authority requirements, or project specifications.
Typical use cases
- Early estimation and tender support.
- BOQ sanity checking and technical review.
- Site discussion before final engineering verification.
- Comparison of alternatives using consistent assumptions.
Result interpretation
Read the recommendation, warning, and confidence sections together. A result without warnings is still not an approval; it only means the entered values did not trigger built-in planning alerts.
Input definitions and typical values
These notes explain what each input means and which values usually produce a more reliable planning result.
Code / standard profile
Selects the planning profile used for conservative defaults. Use the project authority or client standard where known; otherwise use the closest regional profile. Options: GCC project planning, ASHRAE planning, CIBSE planning.
Room area m2
Measured floor area used by the calculation. Use drawing or measured values; small rooms are often 10-30 m2, large commercial zones may be hundreds or thousands of m2.
Room height m
Clear internal height or equipment height. Typical occupied rooms are 2.7-3.2 m; warehouses, atria, and plant rooms can be much higher.
Target air changes ACH
Air changes per hour. Offices may be low single digits; toilets, kitchens, exhaust rooms, and plant rooms often need higher ACH by code and use.
Occupants people
Expected number of people using the space. Use realistic peak occupancy, not only average daily occupancy.
Fresh air per person CFM/person
Fresh air per person. Typical planning values are often 15-25 CFM/person, subject to ASHRAE, CIBSE, local code, and room use.
Cooling load TR
Cooling capacity in refrigeration tons. 1 TR equals about 3.517 kW; use calculated load where possible, not only area rule of thumb.
Supply airflow per ton CFM/TR
Supply airflow per refrigeration ton. A common planning range is 350-450 CFM/TR; 400 CFM/TR is often used for comfort cooling checks.
Design margin %
Design safety margin. 5-15% is common for planning; excessive margin can oversize equipment, cables, pumps, or tanks.
Practical verification checklist
- Confirm the selected standard profile is suitable for the project location and authority.
- Replace sample values with project drawings, schedules, equipment data, or measured site values.
- Review warnings, methodology, and PDF report before using the result outside early planning.
- Verify final decisions against official standards, manufacturer data, consultant specifications, and local approvals.
Related tools
Other tools in HVAC.
Duct Sizing & Velocity Checker
Check duct velocity, equivalent diameter, airflow density, and noise-risk level.
Open Tool
Chilled Water Pipe Sizing Tool
Calculate chilled water flow, pipe velocity, and pressure-loss warning.
Open Tool
Exhaust Fan Sizing Calculator
Estimate exhaust fan capacity from room volume, ACH, equipment count, and margin.
Open ToolCalculation methodology
Compares ACH-based airflow, occupant ventilation airflow, and cooling-ton airflow, then applies design margin to the governing value.
Inputs are treated as planning assumptions. The calculator shows warnings when entered values fall outside practical thresholds or selected standard-profile limits.
Version history
- v1.3.6-prelaunch: Added methodology, standard profile support, version notes, and direct PDF report download.
- v1.3.5: Calculator page added with sample data, warnings, and print-ready report layout.
Stage 2 roadmap: optional saved projects, dashboards, and shared calculation history without forcing login for free use.
Trust and verification
Every result includes assumptions, warning logic, and a downloadable report. Final engineering decisions still need qualified review, local authority approval, manufacturer data, and project specifications.
Worked example
Use the sample data button to load a realistic scenario, then download the PDF report to review inputs, results, methodology, warnings, and disclaimers in one place.