The Fluid Calculator set covers the hydraulics and fluid-dynamics problems engineers and technicians encounter most. Characterize oil performance with the Viscosity Index Calculator, analyze pipe-wall pressure with the Young-Laplace Pressure Calculator, size treatment basins with the Detention Time and Hydraulic Retention Time calculators, and model friction losses in flow systems with the Friction Calculator.
Browse the Popular list to find the most-used tools quickly, or explore the Trending tab for recent picks. Everything here is free, needs no account, and runs on any device.
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Air Flow Rate Calculator From Pressure and DiameterCalculate air flow rate from pressure difference and pipe diameter. Get volumetric flow in m³/s, m³/h and CFM plus velocity using Bernoulli equation.
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Manning's Pipe Flow CalculatorCompute flow rate (discharge), velocity, area and hydraulic radius in a circular pipe using the Manning equation for full or partially full pipes.
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Specific Gravity to Density CalculatorConvert specific gravity (SG) to density. Multiply SG by the reference water density (1000 kg/m³) to get density in kg/m³, g/cm³ and g/L instantly.
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Hydropower Output CalculatorCalculate hydroelectric power output from water flow rate, head, and efficiency using P = ρgQHη. Results in watts and kilowatts.
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Kinematic Viscosity CalculatorCalculate kinematic viscosity (ν) from dynamic viscosity (μ) and density (ρ) using ν = μ/ρ. Get results in m²/s, Stokes, and centistokes.
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Density Altitude CalculatorCalculate density altitude from field elevation, altimeter setting, and OAT using DA = PA + 120 x (OAT - ISA). Quick pilot performance estimate.
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Water Density by Temperature CalculatorCalculate the density of water at any temperature from 0 to 100 °C using the standard empirical polynomial. Results in kg/m³ and g/cm³.
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Water Pressure Loss from Elevation CalculatorCalculate water pressure loss from elevation change using 0.433 psi per foot. Enter elevation in feet and specific gravity to get psi, head, and bar.
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GPM to CFS ConverterConvert gallons per minute (GPM) to cubic feet per second (CFS) instantly. Enter a flow rate and get an accurate CFS value using CFS = GPM / 448.831.
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Acre-Feet to Gallons CalculatorConvert acre-feet to US gallons instantly. Enter acre-feet and get the exact gallon volume using 1 acre-foot = 325,851 gallons.
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CFS to GPM ConverterConvert cubic feet per second (CFS) to gallons per minute (GPM) instantly. Uses 1 CFS = 448.831 US GPM. Free flow-rate conversion tool.
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Liters per Second to GPM ConverterConvert liters per second (L/s) to US gallons per minute (GPM) instantly. Enter a flow rate and get the exact GPM value using the 15.8503 factor.
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Relative Humidity from Dew Point CalculatorCalculate relative humidity (%) from air temperature and dew point using the Magnus formula. Fast, accurate, and free online RH calculator.
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Pump Efficiency CalculatorCalculate pump efficiency from flow rate, head, fluid density and shaft power using η = (ρgQH)/P. Get hydraulic power and efficiency percentage instantly.
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Water Flow From Tank Time CalculatorCalculate the time to fully drain a tank through a hole using Torricelli law. Enter tank area, hole area, liquid height and discharge coefficient.
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Absolute to Gauge Pressure CalculatorConvert absolute pressure to gauge pressure instantly. Enter absolute and atmospheric pressure to find gauge pressure using Pg = Pabs − Patm.
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Water Vapor Pressure CalculatorCalculate the saturation vapor pressure of water at any temperature using the Tetens formula. Get results in kPa, hPa (mbar), and mmHg.
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Hoop Stress Calculator (Thin-Wall Pipe)Calculate hoop (circumferential) and axial stress in a thin-wall pressurized pipe or cylinder using σ = PD/2t. Enter pressure, diameter and wall thickness.
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Pipe Wall Thickness Calculator (Barlow's Formula)Calculate minimum pipe wall thickness from internal pressure, outside diameter, and allowable stress using Barlow formula t = PD/(2S). In inches and mm.
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Gallons per Minute from Meter or Bucket Test CalculatorCalculate gallons per minute (GPM) flow rate from a bucket fill test. Enter container volume and fill time in seconds to get GPM and GPH.
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Pipe Water Velocity Calculator (GPM & Diameter)Calculate water velocity (ft/s) in a pipe from flow rate in GPM and inside diameter in inches. Fast, accurate plumbing and pipe-sizing tool.
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Air Flow Rate (CFM) CalculatorCalculate airflow in CFM from air velocity (ft/min) and rectangular duct dimensions. Uses CFM = velocity × duct area for HVAC sizing.
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Sprinkler Flow Rate CalculatorCalculate fire sprinkler discharge flow rate (GPM) from K-factor and pressure using Q = K times the square root of P. Free hydraulic calculator.
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Water Column to Pressure CalculatorConvert a water column height (feet or inches of water) into pressure in PSI, kPa and bar. Uses ftH2O x 0.4335 and inH2O x 0.03613.
Frequently asked questions
What fluid and hydraulics problems can I solve here?
The collection covers flow analysis, piping design, and fluid properties: calculate how long water stays in a treatment tank with the Detention Time Calculator, find capillary or bubble pressure with the Young-Laplace Pressure Calculator, compare lubricant performance across temperatures with the Viscosity Index Calculator, and size a gas line with the Gas Line Calculator.
Are the fluid calculators free?
Yes — every tool on this page is free to use, with no login or download required. They load instantly on any phone, tablet, or desktop browser.
How accurate are the results?
The tools apply established fluid mechanics and hydraulics equations including the Young-Laplace equation, Darcy-Weisbach friction factors, and standard viscosity index formulas. Results are suitable for preliminary analysis and academic work. For any safety-critical or regulatory application — pipeline design, water treatment compliance, pressure vessel specification — verify calculations against the governing engineering code and have a qualified engineer review the work.
Do you store my inputs?
No. Every calculation runs entirely in your browser. Flow rates, pressures, viscosities, and dimensions you enter are never sent to our servers or saved in any way.
Which fluid calculators do users reach for most?
The Popular list ranks tools by real visitor traffic, so the most-used calculators appear at the top. You can also browse Trending for fast-rising tools, Recently Added for the newest entries, or Last Updated for recently revised calculators.
