Results feed into the area converter above. Use area with airflow to calculate duct velocity: velocity (FPM) = CFM / area (ft²), or velocity (m/s) = (L/s) / area (m²).
Key Conversion Factors
1 m² = 10 000 cm² = 10.764 ft² = 1550.0 in²
1 in² = 6.4516 cm² = 645.16 mm² = 0.000694 ft²
1 yd² = 9 ft² = 1296 in² = 0.8361 m²
Round duct area = π × (D/2)² | Rect. duct area = W × H
Round Duct Cross-Section Areas
| Diameter (in) | Diameter (mm) | Area (in²) | Area (cm²) | Area (ft²) | Area (m²) |
|---|---|---|---|---|---|
| 4 | 102 | 12.57 | 81.1 | 0.0873 | 0.00811 |
| 5 | 127 | 19.63 | 126.7 | 0.1364 | 0.01267 |
| 6 | 152 | 28.27 | 182.4 | 0.1963 | 0.01824 |
| 7 | 178 | 38.48 | 248.3 | 0.2673 | 0.02483 |
| 8 | 203 | 50.27 | 324.3 | 0.3491 | 0.03243 |
| 9 | 229 | 63.62 | 410.4 | 0.4418 | 0.04104 |
| 10 | 254 | 78.54 | 506.7 | 0.5454 | 0.05067 |
| 12 | 305 | 113.10 | 729.7 | 0.7854 | 0.07297 |
| 14 | 356 | 153.94 | 993.2 | 1.069 | 0.09932 |
| 16 | 406 | 201.06 | 1297 | 1.396 | 0.1297 |
| 18 | 457 | 254.47 | 1642 | 1.767 | 0.1642 |
| 20 | 508 | 314.16 | 2027 | 2.182 | 0.2027 |
| 24 | 610 | 452.39 | 2919 | 3.142 | 0.2919 |
Common Rectangular Duct Cross-Section Areas
| Duct Size (in) | Duct Size (mm) | Area (in²) | Area (cm²) | Area (ft²) |
|---|---|---|---|---|
| 8 x 6 | 203 x 152 | 48 | 309.7 | 0.333 |
| 10 x 6 | 254 x 152 | 60 | 387.1 | 0.417 |
| 12 x 8 | 305 x 203 | 96 | 619.4 | 0.667 |
| 14 x 8 | 356 x 203 | 112 | 722.6 | 0.778 |
| 16 x 10 | 406 x 254 | 160 | 1032 | 1.111 |
| 18 x 10 | 457 x 254 | 180 | 1161 | 1.250 |
| 18 x 12 | 457 x 305 | 216 | 1394 | 1.500 |
| 20 x 12 | 508 x 305 | 240 | 1548 | 1.667 |
| 24 x 12 | 610 x 305 | 288 | 1858 | 2.000 |
| 24 x 14 | 610 x 356 | 336 | 2168 | 2.333 |
| 24 x 18 | 610 x 457 | 432 | 2787 | 3.000 |
| 30 x 18 | 762 x 457 | 540 | 3484 | 3.750 |
Floor Area -- Canadian HVAC Design Reference
| Home / Space Type | ft² | m² | Typical Heating Load* | Typical Cooling Load* |
|---|---|---|---|---|
| Condo / apartment | 600 - 1000 | 56 - 93 | 6 - 12 kW | 4 - 8 kW |
| Small detached home | 1000 - 1500 | 93 - 139 | 10 - 18 kW | 6 - 12 kW |
| Average Canadian home | 1500 - 2500 | 139 - 232 | 14 - 26 kW | 8 - 18 kW |
| Large detached home | 2500 - 4000 | 232 - 372 | 22 - 40 kW | 14 - 28 kW |
| Small commercial / retail | 1000 - 5000 | 93 - 465 | 10 - 60 kW | 8 - 50 kW |
| Office floor plate | 5000 - 20000 | 465 - 1858 | 50 - 200 kW | 40 - 160 kW |
| Large retail / warehouse | 20 000+ | 1858+ | 200+ kW | 150+ kW |
*Approximate ranges only. Actual loads depend on climate zone, envelope, occupancy, and orientation. Always perform a full Manual J or heat loss calculation. Use the Heat Load Calculator for accurate sizing.
How to Use the Area Converter
Type a value in ft², m², in², cm², mm², or yd². All other units update instantly. Use the quick-reference presets for common HVAC areas: room sizes, home floor areas, and standard duct cross-sections.
Use the Duct Cross-Section Calculator below the main converter. Toggle between round and rectangular. For round duct, enter the diameter in inches or mm. For rectangular, enter width and height in inches. Results show cross-sectional area in all four units and automatically populate the area converter above.
The round and rectangular duct reference tables give pre-calculated cross-section areas for all standard HVAC duct sizes. Use these to quickly find the area of a specific duct size without manual calculation, then use that area to compute duct velocity from your airflow rate.
Feed converted floor areas in m² into the Heat Load Calculator. Use duct cross-section areas with the Airflow Converter to check duct velocity. Feed floor area into the HRV Ventilation Calculator for ASHRAE 62.2 compliance.
Area Units in HVAC -- Complete Guide
Area measurements appear throughout HVAC design: floor areas drive load calculations and ventilation requirements, duct cross-sections determine air velocity and pressure drop, and envelope areas affect heat loss calculations. Canadian HVAC practice uses both Imperial and metric area units depending on the source, so fluent conversion is essential.
Square Feet to Square Metres -- Floor Area Conversion
The conversion factor is 1 ft² = 0.09290 m², or 1 m² = 10.764 ft². A 2000 ft² home equals 185.8 m². A 10 x 12 ft bedroom (120 ft²) equals 11.15 m². Canadian building permits and energy codes use m² for floor area. Real estate listings and home conversations in Canada still commonly use ft². The Heat Load Calculator accepts room dimensions and calculates floor area in both units automatically.
Duct Cross-Section Area and Air Velocity
Duct velocity equals airflow divided by cross-sectional area: V = Q / A. For Imperial units: velocity (FPM) = CFM / area (ft²). For metric: velocity (m/s) = flow rate (m³/s) / area (m²). A 10-inch round duct has a cross-section of 78.54 in² = 0.5454 ft² = 506.7 cm² = 0.05067 m². At 400 CFM, the velocity is 400 / 0.5454 = 733 FPM (3.73 m/s). SMACNA recommends trunk duct velocities of 600-1200 FPM (3-6 m/s) for residential and up to 2000 FPM (10 m/s) for commercial systems. Use the Duct Sizing Calculator to size ducts against these criteria directly.
Envelope Area for Heat Loss Calculations
Heat loss calculations require the area of each building assembly: walls, windows, roof, floor. These are typically measured in m² for Canadian engineering calculations and ft² for US-based software. A wall 3.66 m wide by 2.44 m tall (12 ft x 8 ft) has an area of 8.92 m² = 96 ft². Multiply by the U-value (W/m²K) and the design temperature difference to get the heat loss through that assembly. The U-Value Converter and R-Value / RSI Converter handle the thermal property conversions that pair with area in these calculations.
Ventilation Rates Per Unit Area
ASHRAE 62.2 residential ventilation requires 0.15 CFM per ft² (0.76 L/s per m²) of occupiable floor area as the area-driven component. ASHRAE 62.1 commercial ventilation specifies per-area rates for low-occupancy spaces: retail at 0.9 L/s/m², offices at 0.3 L/s/m², parking garages at 3.0 L/s/m². Converting these rates requires knowing the floor area in the correct unit. A 500 m² retail floor needs 500 x 0.9 = 450 L/s (953 CFM) of ventilation from the area component alone. Use the Airflow Unit Converter to work with these rates across unit systems.
Frequently Asked Questions
Multiply ft² by 0.09290 to get m². To go the other way, multiply m² by 10.764. Quick reference: 100 ft² = 9.29 m², 1000 ft² = 92.9 m², 2000 ft² = 185.8 m², 2500 ft² = 232.3 m². This conversion is needed whenever Canadian building permits, energy audits, or ASHRAE ventilation rate calculations require m² but the floor plan was drawn in Imperial. Feed the converted area directly into the Heat Load Calculator.
For round duct: area = pi x (diameter / 2)². A 10-inch round duct has area = 3.14159 x 25 = 78.54 in² = 0.5454 ft². For rectangular duct: area = width x height. A 16x10 inch duct has area = 160 in² = 1.111 ft². Use the Duct Cross-Section Calculator in this page to compute and convert any duct size instantly, or look up pre-calculated values in the reference tables above.
The average new single-detached Canadian home is approximately 186 m² (2000 ft²) of finished floor area. Alberta and Ontario tend to build larger, averaging 200-230 m². BC homes average smaller at 160-190 m² due to land costs. Floor area directly drives heating and cooling load estimates -- a rough rule of thumb for a well-insulated Canadian home is 30-45 W/m² (about 10-14 BTU/hr/ft²) of heating capacity. Always do a full heat loss calculation rather than relying on this rule for actual equipment sizing.
ASHRAE 62.2 requires 0.15 CFM/ft² (0.76 L/s/m²) of occupiable floor area as the area-driven ventilation component, added to the occupant-based component. For a 2000 ft² (185.8 m²) home, the area component is 300 CFM (141.6 L/s). ASHRAE 62.1 commercial standards specify per-area rates by space type: 0.3 L/s/m² for offices, 0.9 L/s/m² for retail, 3.0 L/s/m² for parking. Use the HRV Ventilation Calculator for full ASHRAE 62.2 residential compliance calculations.