HVAC, Plumbing, Water & Building Services Calculators

Heating, cooling, ventilation, plumbing, water and building services.

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Air Conditioner BTU CalculatorEstimates the BTU or kilowatt cooling capacity needed to size an air conditioner for a room.

Air Changes Per Hour CalculatorCalculate air changes per hour from room volume and airflow rate for ventilation design with…

Pipe Flow CalculatorThis tool applies the continuity equation for a full, round pipe: Q = A × v, where Q is the…

Pipe Velocity CalculatorFlow velocity is the average speed of fluid moving along the pipe.

All HVAC, Plumbing, Water & Building Services Calculators (39)

Guide to HVAC Calculators

This hub gathers the sizing and flow maths that building-services trades, hydraulic designers and facilities managers reach for when specifying pipes, ducts, pumps, drains and ventilation. The awkward part is that the same job (say "move this much water" or "cool this room") can be attacked from several directions — velocity, head loss, friction factor or channel geometry — and picking the wrong entry point gives a number that looks right but ignores the real constraint.

Sizing pipes and predicting pressure loss

Start with pipe-sizing or velocity when you know flow and want a diameter; move to Darcy-Weisbach, friction-factor and fittings tools once the diameter is fixed and you need the actual pressure drop along the run.

Pipe Sizing for Flow Velocity Calculator Pipe Velocity Calculator Pipe Flow Calculator Friction Loss Calculator Darcy-Weisbach Head Loss Calculator Friction Factor (Moody) Calculator Pressure Drop through Fittings Calculator

Pumps, head and cavitation

Use total dynamic head and pump-head tools to spec against a system curve, pump-power for the energy draw, NPSH to guard against cavitation, and affinity laws when re-rating an existing pump for a new speed or impeller.

Pump Total Dynamic Head (TDH) Calculator Pump Head Calculator Pump Power Calculator NPSH Available Calculator Pump Affinity Laws Calculator Water Hammer Pressure Calculator

Ducts, cooling load and ventilation

Size cooling with BTU and heat-load estimators (BTU-to-kW to translate units), then size the airside with duct area, velocity and sizing tools; use air-changes, ventilation-rate and extractor-fan tools when the driver is air quality rather than temperature.

Air Conditioner BTU Calculator Heat Load Rough Estimator BTU to kW Converter Duct Sizing Calculator Duct Velocity Calculator Air Changes Per Hour Calculator Extractor Fan Size Calculator

Open channels, weirs and stormwater drainage

Reach for Manning (pipe or channel) and trapezoidal-channel tools for gravity flow in partly full sections, weir tools when a measuring or overflow structure sets the level, and inlet-capacity for grated stormwater pits.

Manning Open Channel Flow Calculator Manning Pipe Flow Calculator Trapezoidal Channel Flow Calculator V-Notch Weir Flow Calculator Broad-Crested Weir Flow Calculator Drainage Inlet Capacity Calculator

Water storage, harvesting and irrigation

Use roof-catchment and rainwater-harvesting to estimate supply, tank-days-supply to check how long storage lasts, and the irrigation, sprinkler and pool-turnover tools to distribute or cycle it.

Roof Catchment Calculator Rainwater Harvesting Calculator Tank Days Supply Calculator Irrigation Flow Calculator Sprinkler Spacing Calculator Pool Turnover Rate Calculator Septic Tank Sizing Estimator

Important calculation notice

These calculators are intended for education, estimation and preliminary checks. Verify all inputs, units, assumptions, material properties and applicable standards. Safety-critical or final engineering designs should be checked by a suitably qualified professional.

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HVAC, Plumbing, Water & Building Services Calculators

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All HVAC, Plumbing, Water & Building Services Calculators (39)

Plumbing & Water Supply13 calculators

Pipe Flow & Hydraulics11 calculators

HVAC & Ventilation10 calculators

Open Channel & Drainage5 calculators

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