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.
Blast radius calculator
Find the distance at which a charge still produces a chosen peak overpressure, such as about 7 kPa for broken windows or 35 kPa for severe building damage.
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Bohr model calculator
Hydrogen's ground state sits at −13.6 eV and one Bohr radius; the next level sits at −3.4 eV and four Bohr radii.
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Boost converter calculator
With 12 V in and a 0.5 duty cycle, an ideal boost converter delivers 24 V, a gain of 2. Enter input voltage and duty cycle as a fraction to get the output, gain…
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Bridge rectifier calculator
120 V RMS through 0.7 V silicon diodes gives a DC peak of 120 times the square root of 2, minus two diode drops.
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Broad-crested weir calculator
A 1.5 m crest under 0.3 m of head forms critical flow at a depth of 0.2 m, two thirds of the head.
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Column buckling calculator
Doubling a column's unsupported length cuts its Euler buckling load to a quarter, because length is squared.
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Bullet energy calculator
An 8 g bullet at 400 m/s carries 640 J, and doubling the speed would quadruple that energy. Enter mass in kilograms and velocity in metres per second to get…
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Buoyancy experiment calculator
A 2 kg object of density 500 kg/m³, held fully under water of 1,000 kg/m³, feels 39.24 N of buoyancy against 19.62 N of weight, so it floats.
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Capacitance calculator
Plates of 0.01 m² with a 0.001 m gap in vacuum give 8.854 × 10⁻¹¹ F; double the area or halve the gap and the capacitance doubles.
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Capacitor calculator
Two 10 × 10 cm plates 1 mm apart in vacuum, entered as 0.01 m² and 0.001 m, have a capacitance of 8.8541878128 × 10⁻¹¹ F.
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Capacitor charge time
With 1 kΩ and 1 µF the time constant is 1 ms, and a 5 V supply charges the capacitor to 2.5 V after ln 2 time constants.
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Carburetor CFM calculator
A 350 cubic-inch four-stroke at 6,000 rpm with 85 % volumetric efficiency needs about 516 CFM of carburetor airflow.
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Car mass center calculator
Front wheel readings rising from 4,000 to 4,140 when the rear is lifted 0.25 m put a car's centre of mass 0.5 m above the ground.
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Centrifuge speed calculator
Turn a protocol's 1,000 × g at a 10 cm rotor radius into the rpm to set, using standard gravity of 9.80665 m/s².
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Cloud base calculator
A temperature of 20 °C with a dew point of 12 °C puts the cloud base 1,000 m up: 125 m for every degree of spread.
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Compton scattering calculator
A photon scattered at 90° by an electron at rest gains exactly one Compton wavelength, about 2.426 pm, and backscatter at 180° doubles that.
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Compton wavelength calculator
The electron's rest mass of 9.1093837015 × 10⁻³¹ kg gives a Compton wavelength of about 2.426 pm, matching the tabulated value.
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Contact lens vertex calculator
A −8 D glasses prescription at 12 mm becomes about −7.30 D at the cornea, while +10 D at 13 mm needs about +11.49 D.
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Crawl ratio calculator
A 4.46 first gear, a 2.72 low range and 4.10 axles multiply to a crawl ratio of about 49.74, close to 50:1.
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Crossover frequency calculator
A 1 kΩ resistor with a 1 µF capacitor sets a −3 dB corner at 1,000 divided by 2π hertz. Enter R in ohms and C in farads to get the corner frequency, the angular…
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Curie's law calculator
A sample with a Curie constant of 2.4 K in a 500 A/m field at 300 K magnetizes to 4 A/m. Enter the Curie constant, the applied field and the absolute…
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Cv flow calculator
A valve with a Cv of 10 and a 4 psi drop passes exactly 20 US gallons per minute of water. Enter the catalog Cv, the pressure drop and the specific gravity to…
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Cyclotron frequency calculator
A charge of 1 coulomb with 1 kilogram of mass in a 1 tesla field circles at about 0.159 hertz. Enter charge, mass and field strength to get the frequency, the…
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Daylight hours calculator
At the equator every day has 12 hours of daylight, while toward the poles a summer day stretches to 24 and a winter day shrinks to 0.
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dB gain calculator
A voltage that rises from 1 to 10 is a gain of 20 dB, while the same tenfold step in power is 10 dB.
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Debye length calculator
A plasma at 10,000 K with 10¹⁶ electrons per cubic metre shields a charge over less than a tenth of a millimetre.
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Cylinder density calculator
A solid cylinder with mass 1, diameter 2 and height 1 has a volume of π and a density of 1 over π, in matching units.
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Density mass volume calculator
A mass of 12 in a volume of 3 has a density of 4. Enter any two of mass, volume and density, leave the unknown blank, and get the missing value plus a label…
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Diffraction calculator
Light of 500 nm passing a 0.1 mm slit puts its first dark fringe a little more than a quarter of a degree off the axis.
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Electric dipole calculator
Halve the distance to a dipole and the field on its axis grows eight times, while the potential grows four times.
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Displacement calculator
A body starting at 10 m/s and speeding up at 2 m/s² for 5 seconds ends 75 metres from where it began.
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Drift velocity calculator
A current of 1.6 A through a 1 mm² wire holding 10²⁸ conduction electrons per cubic metre drifts at only 1 millimetre per second.
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Earth curvature calculator
Over 20,000 m the surface falls a few tens of metres, but from an eye height of 1.7 m part of that bulge is still in view.
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Heat exchanger effectiveness-NTU calculator
A counterflow exchanger with an NTU of 1 and a capacity ratio of 0.5 delivers a little over half of the maximum possible heat transfer.
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Elastic constants calculator
For steel, a Young's modulus of 200 GPa and a Poisson's ratio of 0.3 are enough to fix the shear and bulk moduli too.
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Electric motor torque calculator
A 1.5 kW motor turning at 1,500 rpm delivers about 9.549 newton-metres at the shaft. Enter the power in watts and the speed in revolutions per minute to get the…
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Electrical mobility
A carrier drifting at 5 centimetres per second in a field of 100 volts per metre has a mobility of 0.0005 square metres per volt-second.
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E=mc² calculator
One kilogram at rest holds nearly 9 × 10¹⁶ joules, its mass times the speed of light squared. Enter a rest mass in kilograms to get its rest energy in joules…
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Energy to wavelength calculator
A photon carrying 10⁻¹⁹ joules has a vacuum wavelength of about 2 micrometres. Enter a photon energy in joules to get its wavelength in metres, worked out from…
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Escape velocity calculator
Leaving the Earth, with 5.972 × 10²⁴ kg and a radius of 6,371,000 m, takes a little over 11 kilometres per second.
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Excess electrons calculator
A charge of −3.2 × 10⁻¹⁸ coulombs is 20 extra electrons when you use the classroom value of 1.6 × 10⁻¹⁹ coulombs.
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Exoplanet calculator
Around a star of one solar mass, a planet at 1 AU completes its orbit in 365.25 days. Enter the star's mass plus either the orbital period in days or the…
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Fan airflow calculator
A 0.4 m fan at 1500 rpm pushes air forward at 10 metres per second in the ideal model, a little over 1 cubic metre per second.
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Fermi level calculator
Copper, with about 8.47 × 10²⁸ conduction electrons per cubic metre, has a Fermi energy near 7 electronvolts.
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Flow rate calculator
A section of 0.01 square metres with fluid moving at 1.5 metres per second carries 0.015 cubic metres per second.
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Foot-pounds of energy calculator
Muzzle energy in foot-pounds is the weight in grains times the speed in feet per second squared, divided by 450240, the formula printed beside factory load…
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Free fall distance calculator
An object dropped from rest falls 19.6 metres in 2 seconds when gravity is 9.8 m/s², with air resistance ignored.
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Free fall height calculator
If a stopwatch shows a 2-second drop under 9.8 m/s² of gravity, the object was released 19.6 metres up.
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Frequency of light calculator
A 1-metre wavelength in vacuum gives 299,792,458 Hz, and a 500 nm green line comes out near 6 × 10^14 Hz, the scale of visible light.
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Friction coefficient calculator
Divide the friction force by the normal force and get the coefficient μ: 20 N of friction against 50 N of normal force gives 0.4.
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Friction factor calculator
With a Reynolds number of 100,000 and a relative roughness of 0.0002, the Darcy friction factor is 0.019003236842, in turbulent flow.
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Froude number calculator
Water moving at 2 m/s with a depth of 1 m under Earth's 9.81 m/s² gives a Froude number of 0.6385508568, a subcritical flow.
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Gear ratio RPM calculator
A 1000 rpm motor turning a 20-tooth gear that drives a 40-tooth gear gives a ratio of 2 and 500 rpm at the output.
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Gay-Lussac's law calculator
Heat a sealed sample at 1 atm from 300 K to 600 K and its pressure doubles to 2 atm. Give the starting pressure in any unit and both temperatures in kelvin; the…
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Generator power calculator
A 230 V single-phase generator delivering 10 A at a power factor of 0.8 gives 1840 W, or 1.84 kW, of real power.
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Ground speed calculator
At 250 knots true airspeed with a 40-knot tailwind, ground speed is 290 knots; turn that wind into a headwind and it drops to 210.
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Hair diffraction calculator
A 500 nm laser, a screen 2 m away and dark fringes 10 mm apart give a hair diameter of 0.0001 m, or 100 micrometres.
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Hall coefficient calculator
12 mV of Hall voltage across a strip half a millimetre thick, at 2 mA in a quarter-tesla field, gives a Hall coefficient of 0.012 m³/C.
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Heisenberg uncertainty calculator
Confine a particle to 10^-10 m, an atomic scale, and its momentum spread can be no smaller than about 5 × 10^-25 kg·m/s.
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Helical coil inductance calculator
Ten turns on a 0.0254 m radius spread over 0.0508 m, a 1-inch by 2-inch air coil, give 3.44827586207 µH.
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