Fluid Calculator

  • Hot Tub Volume Calculator
    Calculate how many gallons of water your hot tub holds. Enter the shape and dimensions to estimate volume in gallons, liters and cubic feet.
  • Horizontal Cylindrical Tank Volume Calculator
    Calculate the liquid volume in a horizontal cylindrical tank for any fill height. Get partial-fill volume, fill %, liters and US gallons instantly.
  • Bucket Volume Calculator
    Calculate the volume of a tapered bucket from its top diameter, bottom diameter and height. Get results in liters, US gallons and UK gallons instantly.
  • Pipe Flow Velocity Calculator
    Calculate fluid velocity in a pipe from flow rate and inner diameter using v = Q / (π/4 × D²). Free, instant pipe flow speed calculator.
  • Continuity Equation Flow Rate Calculator
    Calculate volumetric flow rate Q = A·v and downstream velocity using the continuity equation A₁v₁ = A₂v₂ for circular pipes. Free and instant.
  • GPM Flow Rate Calculator (Pipe)
    Calculate pipe flow rate in GPM from flow velocity (ft/s) and inside diameter (inches). Free gallons-per-minute calculator using velocity × area × 448.831.
  • Dynamic Pressure Calculator
    Calculate dynamic pressure q = ½ρv² from fluid density and flow velocity. Get instant results in pascals and kilopascals for aerodynamics and fluid flow.
  • Volumetric Flow Rate Calculator
    Calculate volumetric flow rate Q from cross-sectional area A and flow velocity v using Q = A·v. Get results in m³/s, L/min and GPM instantly.
  • Torricelli's Law Calculator
    Calculate the efflux velocity of fluid escaping a hole using Torricelli's Law, v = √(2gh). Enter fluid height and gravity to get speed in m/s.
  • Flow Continuity Equation Calculator
    Solve the fluid continuity equation A1·v1 = A2·v2. Enter inlet area, inlet velocity, and outlet area to find outlet velocity and volumetric flow rate.
  • Darcy-Weisbach Head Loss Calculator
    Calculate pipe friction head loss with the Darcy-Weisbach equation: h_f = f·(L/D)·(v²/2g). Enter friction factor, length, diameter and velocity.
  • Buoyant Force Calculator
    Calculate buoyant (upthrust) force using Archimedes' principle: F = ρ·V·g. Enter fluid density, displaced volume and gravity to get the force in newtons.
  • Oxygen Tank Duration Calculator
    Estimate how long an oxygen tank will last from gauge pressure, cylinder tank factor, and flow rate (L/min). Quick remaining-time calculator.
  • Water Weight Calculator
    Calculate the weight of water from any volume. Convert gallons, liters, mL or fluid ounces into pounds, kilograms, grams and ounces instantly.
  • Kinematic Viscosity Unit Conversion Calculator
    Convert kinematic viscosity between m2/s, Stokes, centistokes, in2/s and ft2/s instantly. Enter one value and see all common units at once.
  • Dynamic Viscosity Unit Conversion Calculator
    Convert dynamic (absolute) viscosity between Pa.s, mPa.s, poise, centipoise, kgf.s/cm2, lbf.s/ft2 and more. Instant all-unit conversion.
  • Evaporation Rate Calculator
    Calculate water evaporation rate from a free surface using gₕ = Θ·A·(xₛ − x). Enter the evaporation coefficient, area and humidity ratios.
  • Surface Tension Calculator
    Calculate surface tension (γ) from the force on a wire and its wetted length using γ = F / (2L). Free physics calculator with mN/m output.
  • Immersed (Apparent) Weight Calculator
    Calculate the immersed or apparent weight of an object in a fluid using buoyancy. Enter mass, volume, fluid density and gravity to get apparent weight in newtons.
  • Volumetric Flow Rate Conversion Calculator
    Convert volumetric flow rate between 21 units (L/min, m3/h, CFM, US/UK GPM, mL/s and more) instantly. Free, accurate SI-based flow rate converter.
  • IV Drip Rate Calculator
    Calculate IV infusion drip rate in drops per minute and seconds per drop from fluid volume, infusion time or hourly rate, and the drop-set factor (20 or 60 gtt/mL).
  • Buoyant Force Calculator
    Calculate buoyant force from fluid density, displaced volume, and gravity using Archimedes' principle (Fb = ρgV). Free, instant, with worked example.
  • y+ Calculator
    Calculate y+ (dimensionless wall distance) for CFD meshing from density, viscosity, wall shear stress and first cell distance. Includes friction velocity.
  • Kinematic Viscosity of Air Calculator
    Calculate the kinematic viscosity of air (ν = μ / ρ) from dynamic viscosity and air density. Get results in m²/s and centistokes instantly.

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