Ventilation Calculators: Airflow, Ducts and Fans

Plan ventilation systems with calculators for airflow requirements, fan power, duct area, and the number of diffusers or grids needed. Use Ventilation Airflow Requirement and Ventilation per Number of People to estimate fresh-air needs for a space and its occupants. Area of Rectangular Duct helps with duct planning, while Ventilation Diffuser Count and Ventilation Grid Count help lay out air distribution.These tools are for HVAC designers, engineers, contractors, and building owners making preliminary ventilation estimates. Check your results against applicable codes and project specifications before finalizing a design.

Area of Rectangular Duct

Enter the side dimensions, length and quantity of a rectangular duct to get the total sheet-metal surface area, connector strip (shina) length and corner piece count, with an optional seam allowance.

Duct Pressure Drop

Estimate the pressure drop in a rectangular or circular ventilation duct from its size, length, airflow and fittings. Enter duct dimensions, airflow rate and friction factor to get friction loss, fitting loss and total pressure drop in Pa, mm H2O and in. w.g.

Ventilation Diffuser Count

Calculate how many air diffusers you need for a ventilation system. Enter the total air flow (m³/h), the air speed (m/s), and the diffuser diameter to get the required diffuser count.

Ventilation Power

Calculate the required ventilation air flow rate (m³/h) from room area, ceiling height, and desired air changes per hour. Enter three values to size fans, diffusers, and ductwork correctly.

Ventilation Airflow Requirement

Calculate the required ventilation airflow (m³/h) from the room type, floor area, and ceiling height. Enter the room type, area in m², and height in cm to get the recommended fan performance instantly.

Ventilation Grid Count

Calculate the number of ventilation grids needed from the air flow rate (m³/h), air speed (m/s), and the open area of one grid (m²). Enter your values and get the required grid count instantly.

Ventilation per Number of People

Estimate the required ventilation airflow from the number of people in a room and their activity level. Enter the occupant count, pick an activity level, and get the airflow in m³/h.

Wall Heat Loss

Calculate the rate of heat loss through a wall using the U-value, wall area and indoor/outdoor temperatures. Enter values in metric or imperial units and get results in watts, BTU/hr and kWh per day.

Fan Affinity Laws

Calculate fan airflow, pressure, and power at a new speed using the fan affinity laws. Enter the original speed, airflow, pressure, and power, plus the new speed in rpm.

LMTD

Calculate the log mean temperature difference (LMTD) of a heat exchanger from the four terminal temperatures. Choose counterflow or parallel flow and enter the hot and cold inlet/outlet temperatures in °C, °F or K.