Science
1,125 science calculators for chemistry, physics, biology, astronomy and the Earth sciences. Each one states the relation it uses and the units it expects, so class problems, lab work and quick checks come out right, free in your browser.
Helmholtz resonator calculator
A 1.87-litre cavity with a neck 3.14 cm² in area and 5 cm long resonates at about 100 Hz in air at 343 m/s.
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Hoop stress calculator
A pipe at 1 MPa with a 0.2 m bore and a 5 mm wall carries a hoop stress of 20,000,000 Pa, the circumferential pull that tries to split it along a seam.
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Hubble's law calculator
A galaxy 100 megaparsecs away recedes at 7000 km/s when the Hubble constant is 70 km/s per megaparsec.
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Hydraulic gradient calculator
Heads of 20 m and 16 m at two wells 100 m apart give a hydraulic gradient of 0.04, with groundwater moving from the first well toward the second.
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Hydraulic radius calculator
A section with 2 m² of flow area and 4 m of wetted perimeter has a hydraulic radius of 0.5 m. Divide area by wetted length to get the characteristic length that…
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Ideal gas temperature calculator
One mole of gas at 101325 Pa filling 0.022414 m³ sits at about 273 K. Enter pressure in pascals, volume in cubic metres and the amount in moles; the gas…
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Ideal gas pressure calculator
One mole of gas at 298.15 K in 0.024465 m³ exerts about 101325 Pa, roughly one standard atmosphere.
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Ideal transformer calculator
A 240 V primary with 1000 turns and a turns ratio of 0.1 gives 24 V on a 100-turn secondary, a step-down transformer.
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Immersed weight calculator
A 50 N object displacing 0.002 m³ of water at 1000 kg/m³ reads 30.38 N on a scale, because the water pushes up with 19.62 N.
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Insertion loss calculator
Feed 1 W into a cable or filter, measure 0.5 W at the far end, and the insertion loss is 3.01029995664 dB.
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Internal resistance calculator
A 12 V battery that reads 11 V while delivering 2 A has an internal resistance of 0.5 Ω, with 1 V lost inside the cell.
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Intrinsic carrier concentration calculator
Textbook silicon values at 300 K, with densities of states of 2.8 × 10^25 and 1.04 × 10^25 per cubic metre and a 1.12 eV bandgap, give an intrinsic carrier…
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Knudsen number calculator
Sea-level air, whose molecules travel about 65 nm between collisions, flowing in a 1 mm channel gives a Knudsen number of 0.000065: plainly continuum flow.
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J-pole antenna calculator
At 146 MHz on the 2-metre band, a J-pole needs a 1.0266865 m half-wave radiator, a 0.51334325 m matching stub and a 1.54002975 m long element.
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Kepler third law
A satellite 42,164,000 m from the centre of Earth, whose mass is 5.9722 × 10^24 kg, takes 86163.3432753 seconds per orbit: one sidereal day.
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Laser spot size calculator
A 632.8 nm helium-neon beam 5 mm wide, focused by a lens with a 0.1 m focal length, comes to a spot 0.0000161141196782 m across.
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LED current calculator
A 5 V USB rail, a red LED with a 2 V drop and a 150 Ω resistor give 0.02 A through the diode, with 3 V across the resistor.
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Lensmaker's equation
Get the focal length of a thin lens from its material, the medium around it and its two curved faces: a lens of index 1.5 in air with radii of 0.1 and -0.1 m…
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Linear actuator force calculator
A motor torque of 1 N·m on a screw with a 5 mm lead at 0.9 efficiency pushes with more than 1000 N.
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Lorentz force calculator
A 2 C charge moving at 3 m/s along x, with a 4 V/m electric field along y and a 5 T magnetic field along z, feels 22 N along minus y.
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Lumen calculator
A 100 candela source shining into 2 steradians sends out 200 lumens. Enter the luminous intensity and the solid angle of the beam and get the luminous flux…
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Magnetic declination calculator
If a landmark lies at 50° true and your compass reads 45°, the local declination is 5° east. Enter both bearings of the same point and get the signed offset…
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Magnetic dipole moment calculator
A loop carrying 2 A around an area of 0.5 m² has a magnetic dipole moment of 1 A·m². Enter the current and the enclosed area of a single flat loop to get its…
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Magnetic force on a current-carrying wire
A wire carrying 2 A along 0.5 m of a 0.4 T field, at 90° to it, feels a force of 0.4 N. Enter current, length, field and the angle in degrees to get the force…
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Magnetic moment calculator
A 10-turn coil carrying 2 A around 0.05 m² has a magnetic moment of 1 A·m². Enter current, number of turns and loop area to get the moment of a whole coil, not…
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Magnitude of acceleration
Components of 3 and 4 m/s² along x and y give an acceleration of 5 m/s². Enter the axis components, leave the third empty for motion in a plane, and get the…
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Manometer calculator
A 0.2 m difference in a water column, at 1000 kg/m³ and 9.81 m/s², means 1962 Pa. Enter the column height difference, the liquid density and gravity to turn a…
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Mass to density calculator
An object of 12 kg that fills 3 m³ has a density of 4 kg/m³. Enter the mass you weighed and the volume you measured to get the density, with a clear refusal…
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Maximum height projectile motion
A ball launched at 20 m/s and 45° under a gravity of 9.8 m/s² rises just over 10 m above its launch point.
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Mixed-air temperature calculator
Mixing 2 kg/s of air at 10 °C with 2 kg/s at 30 °C gives a blend at 20 °C. Enter the temperature and mass flow of each stream to get the adiabatic mixed-air…
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AHU mixed air temperature
In an air-handling unit, 0.4 kg/s of outdoor air at 35 °C mixed with 1.6 kg/s of return air at 24 °C reaches the coil at 26.2 °C.
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AM modulation index calculator
A 2 V message on a 5 V carrier gives a modulation index of 0.4, or 40 %. Enter both peak amplitudes in the same unit to see whether an AM signal is…
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Mohr's circle calculator
Normal stresses of 80 and 20 with a shear of 40 give principal stresses of 100 and 0 and a maximum shear of 50, in whatever unit you use.
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MOSFET threshold voltage
A flat-band voltage of -0.9 V, a body coefficient of 0.5 and a surface potential of 0.7 V, with the body tied to the source, give a threshold just over two…
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NE555 astable calculator
Timing resistors of 4.7 kΩ and 10 kΩ with a 100 nF capacitor make an NE555 astable run at a duty cycle of 59.5 %.
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Newton's third law calculator
Push on a wall with 12 N to the right and the wall pushes back with 12 N to the left, written as -12.
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NPSH calculator
Water at 200000 Pa absolute suction pressure, with a vapor pressure of 2000 Pa and a velocity head of 0.5 m, has just over twenty metres of NPSH available.
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Ohm's law current calculator
A 12 V battery across a 4 Ω heater drives 3 A. Enter the voltage across a load and its resistance to get the direct current in amperes, with the sign kept for…
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Ohm's law power calculator
A 12 V supply pushing 2 A delivers 24 W. Enter any two of voltage, current and resistance to get the power in watts and see which identity was used: V times I…
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Open channel flow calculator
A channel with 3 m² of flow area, a hydraulic radius of 0.6 m, a slope of 0.001 and a roughness of 0.015 carries about four and a half cubic metres per second.
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Optical density calculator
If 100 units of light reach a sample and 10 get through, transmittance is 0.1 and optical density is exactly 1.
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Parallel capacitor calculator
Capacitors of 1, 2.2 and 4.7 µF in parallel, entered as 0.000001, 0.0000022 and 0.0000047 farads, add up to 0.0000079 farads.
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Parallel inductors calculator
Two 10 H coils in parallel act as a single 5 H inductor, and 4, 6 and 12 H together give 2 H. Enter the inductance of each branch in henries and get the…
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Particle velocity calculator
A particle with 9 J of kinetic energy and a mass of 2 kg moves at 3 m/s. Enter the energy in joules and the mass in kilograms to get the speed of anything from…
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Performance coefficient calculator
A refrigerator that removes 400 J of heat from its cold side using 100 J of work has a COP of 4. Enter the heat absorbed and the work supplied and get the…
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Photoelectric effect calculator
A 1000 THz photon carries 6.62607015 × 10⁻¹⁹ J, so a metal with a work function of 3 × 10⁻¹⁹ J releases electrons that keep the surplus as kinetic energy.
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Photon energy calculator
A photon with a 500 nm wavelength carries nearly 4 × 10⁻¹⁹ joules. Enter a wavelength in metres or a frequency in hertz and get the energy from Planck's…
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Piston force calculator
A pressure of 1 MPa on a 0.1 m bore pushes the piston with almost 8 kN. Enter the cylinder pressure in pascals and the bore in metres to get the full-bore force…
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Piston speed calculator
An 86 mm stroke at 6000 rpm gives a mean piston speed of 17.2 m/s. Enter the stroke in millimetres, metres or inches and the crank speed to get the average in…
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Pneumatic cylinder force calculator
At 6 bar of shop air, a cylinder with a 0.05 m bore pushes out with about 1178.1 N. Enter supply pressure in pascals and bore in metres to get the extension…
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Polar moment of inertia calculator
A solid shaft 0.1 m across has a polar moment of about 9.817 × 10⁻⁶ m⁴. Enter the outer diameter in metres to get J = πd⁴/32, the figure that goes into…
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Pounds per minute converter
Sixty pounds per minute is exactly 0.45359237 kg/s, because the minute cancels and only the exact pound is left.
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Pounds per square inch converter
One psi is about 6894.757293168 pascals, or 0.068947572932 bar. Type a tyre, compressor or hydraulic reading in pounds per square inch and get pascals, bar and…
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Prandtl-Meyer expansion calculator
At Mach 2 in air, with γ of 1.4, the flow has turned about 26.38° from sonic conditions and the Mach angle is 30°.
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Principal stress calculator
With 80 on the x-face, 20 on the y-face and a shear of 40, the principal stresses are 100 and 0. Enter the two normal stresses and the in-plane shear in one…
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Projectile motion calculator
A ball launched at 20 m/s and 45° from 10 m up peaks about 20 m above the ground. Enter speed, angle and launch height to get the range, the maximum height and…
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Pulley calculator
A 400 N load shared by 4 supporting rope segments needs only 100 N of pull. Enter the load and the number of segments to get the mechanical advantage, the rope…
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Quantum number calculator
The numbers 2, 1, 0 and +1/2 describe a valid electron in a 2p orbital, which holds 2 electrons. Enter n, l, ml and ms to check them against the selection rules…
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Projectile motion range calculator
On level ground a launch at 45° goes farthest, because the range then reduces to speed squared over g.
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RC circuit calculator
With 5 V through 1 kΩ into 1 µF, the capacitor reaches about 3.16 V after 1 ms, exactly one time constant.
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