Science & Engineering
Physics and electronics calculators: Ohm's law, resistor color codes, density, speed and distance, energy and more, with the formulas shown.
555 Timer Calculator
Calculate 555 timer astable frequency, period, high and low times and duty cycle from R1, R2 and the timing capacitor. Free oscillator design helper.
Absolute Humidity Calculator
Calculate absolute humidity in grams of water vapor per cubic meter from air temperature and relative humidity. Fast, free and works in your browser.
Allele Frequency Calculator
Find allele frequencies from genotype counts. Enter the number of AA, Aa and aa individuals to get the A and a allele frequencies and allele totals.
Angular Acceleration Calculator
Find angular acceleration from a change in angular velocity over time, and the torque from a moment of inertia. Enter start and end rad/s and the time.
Angular Size Calculator
Calculate the apparent angular size of any object from its real size and distance. Get the result in degrees, arcminutes and arcseconds.
Angular Velocity Calculator
Convert between RPM, rad/s and deg/s, and find tangential speed from a radius. Enter rpm or radians per second to relate every rotational measure.
Avogadro's Law Calculator
Solve Avogadro's Law V1/n1 = V2/n2 for the missing volume or moles at constant temperature and pressure. Enter any three values and get the fourth.
Battery Life Calculator
Estimate how long a device runs on a battery from its capacity in mAh and current draw in mA. Includes a real-world efficiency factor for an honest figure.
Bernoulli Equation Calculator
Solve Bernoulli's equation for the downstream pressure from density, upstream pressure, two velocities and two elevations for steady incompressible flow.
Boyle's Law Calculator
Solve Boyle's Law P1V1 = P2V2 for the missing pressure or volume at constant temperature. Enter any three values in any consistent units and get the fourth.
Capacitive Reactance Calculator
Calculate the capacitive reactance Xc of a capacitor at any frequency with Xc = 1 / (2 pi f C). Enter frequency and capacitance to get ohms instantly.
Capacitor Code Calculator
Decode capacitor codes like 104 or 223 into pF, nF and uF instantly. Reads 2-digit and 3-digit codes plus tolerance letters. Free electronics tool.
Cell Doubling Time Calculator
Calculate cell or bacterial doubling time from two counts and the elapsed time. Get the number of generations, the doubling time and the growth rate constant.
Centripetal Force Calculator
Find centripetal force and acceleration for circular motion from mass, radius and speed. Enter linear speed or angular velocity to get force in newtons.
Charles's Law Calculator
Solve Charles's Law V1/T1 = V2/T2 for the missing volume or temperature at constant pressure. Enter any three values, set Kelvin or Celsius, get the fourth.
Codon Translator
Translate an mRNA or DNA sequence into amino acids. Read codons in triplets, get the protein in one and three letter codes, and find the stop codon.
Combined Gas Law Calculator
Solve the combined gas law P1V1/T1 = P2V2/T2 for any missing value. Enter five of the six, set Kelvin or Celsius, and get the sixth instantly.
Compass Bearing Calculator
Convert between whole-circle azimuth and quadrant bearings like N30E, and find the back azimuth. Enter an azimuth or a quadrant bearing to convert.
COP Calculator
Calculate the COP of a refrigerator or heat pump. COP = heat moved / work input. Enter the heat transferred and work to compare cooling and heating performance.
Coulomb's Law Calculator
Calculate the electrostatic force between two point charges with Coulomb's law, F = k q1 q2 / r squared. Shows attract or repel. Free physics calculator.
Critical Angle Calculator
Find the critical angle for total internal reflection from two refractive indices. Critical angle = asin(n2/n1), in degrees and radians. Free and instant.
Cut and Fill Calculator
Estimate earthwork cut or fill volume by the average end area method. Enter two cross-section areas and the length to get cubic feet and cubic yards.
Dalton's Law Calculator
Apply Dalton's Law of partial pressures. Sum partial pressures into a total with mole fractions, or split a total pressure by mole fraction. Free online tool.
Darcy-Weisbach Calculator
Calculate pipe friction head loss and pressure drop with the Darcy-Weisbach equation from friction factor, length, diameter, velocity and fluid density.
Decibel Calculator
Add sound levels in decibels and convert between ratios and dB. Combine noise sources logarithmically and switch between power and amplitude ratios.
Decibel Gain Calculator
Calculate gain in decibels from a voltage or power ratio, or convert a dB value back to a linear ratio. Free electrical and audio engineering tool.
Density Altitude Calculator
Calculate density altitude from pressure altitude and outside air temperature. Uses the standard pilot approximation and shows the ISA temperature.
Density Calculator
Calculate density, mass or volume from the other two using density = mass / volume. Supports grams, kilograms, cubic centimetres, litres and more.
Dew Point Calculator
Calculate the dew point from temperature and relative humidity using the Magnus formula. Get the dew point in both Celsius and Fahrenheit instantly.
Dilution Calculator
Solve the dilution equation C1V1 = C2V2 for any one unknown. Find the stock volume to pipette or the final concentration for any solution dilution.
Diopter Calculator
Convert between optical power in diopters and focal length, P = 1/f. Also add up lens powers placed together. Results in meters and centimeters. Free.
DNA to mRNA Converter
Transcribe a DNA sequence into mRNA online. Pick the coding or template strand, get the base for base RNA result, and view the complementary DNA strand.
Efficiency Calculator
Calculate energy or work efficiency as output divided by input times 100. Enter any two values to find the third plus the energy lost. Free physics tool.
Empirical Formula Calculator
Find the empirical formula from percent composition or masses. Enter each element percent, like 40% C and 6.7% H, to get the lowest whole number ratio.
Escape Velocity Calculator
Calculate escape velocity from any planet, moon or star with v = sqrt(2GM/r). Pick Earth, Mars or Jupiter presets or enter mass and radius. Free tool.
Flow Rate Calculator
Calculate volumetric flow rate through a round pipe from diameter and velocity, or find velocity from flow rate. Results in m3/s, L/min and GPM.
Force Calculator
Solve Newton's second law online. Enter any two of force, mass or acceleration and get the third, in newtons, kilograms and metres per second squared.
Gay-Lussac's Law Calculator
Solve Gay-Lussac's Law P1/T1 = P2/T2 for the missing pressure or temperature at constant volume. Enter any three values, set Kelvin or Celsius, get the fourth.
Gravitational Force Calculator
Calculate the gravitational force between two masses with Newton's law of universal gravitation, F = G m1 m2 / r squared. Free physics calculator.
Half-Life Calculator
Solve radioactive decay with N = N0 times one half raised to t over T. Enter any three of initial, remaining, half-life and time to find the fourth.
Hardy-Weinberg Calculator
Find Hardy-Weinberg genotype frequencies from one allele or genotype value. Enter p, q, p squared or q squared to get AA, Aa and aa frequencies.
Heat Engine Efficiency Calculator
Calculate Carnot and actual heat engine efficiency. Carnot = 1 - Tc / Th from reservoir temperatures, actual = work out / heat in from energy values.
Heat Index Calculator
Calculate the heat index or feels like temperature from air temperature and humidity using the NWS Rothfusz regression. Get results in F and C.
Heat Transfer Calculator
Calculate steady state heat conduction through a wall or material with Q = k A deltaT / d. Enter conductivity, area, temperature difference and thickness.
Henderson Hasselbalch Calculator
Calculate buffer pH with the Henderson Hasselbalch equation. Enter pKa and the base and acid concentrations, or a pH and pKa, to find the pH or the ratio.
Hohmann Transfer Calculator
Calculate Hohmann transfer delta-v between two circular orbits, plus the transfer time. Enter the central mass and both orbit radii to size each burn.
Hookes Law Calculator
Solve Hookes law F = k x x for spring force, constant or displacement. Enter any two values to find the third plus the elastic potential energy stored.
Hydraulic Radius Calculator
Calculate hydraulic radius, flow area and wetted perimeter for full pipes, open rectangular channels and full rectangular ducts. SI units, instant results.
Ideal Gas Law Calculator
Solve the ideal gas law PV = nRT for pressure, volume, moles or temperature. Enter any three values, pick your units in atm, kPa, L, m3, K or C.
Inclined Plane Calculator
Calculate inclined plane mechanical advantage, effort force and angle from ramp length and height. Effort equals weight times height over slope length.
Inductive Reactance Calculator
Calculate the inductive reactance Xl of an inductor at any frequency with Xl = 2 pi f L. Enter frequency and inductance to get the reactance in ohms.
Kinetic Energy Calculator
Calculate kinetic energy, mass or velocity using KE = 1/2 m v^2. Enter any two values in SI units (kg, m/s, joules) to solve for the third.
Latent Heat Calculator
Calculate the heat for a phase change with Q = m L. Enter mass and the latent heat of fusion or vaporization to get the energy in joules and kilojoules.
LED Resistor Calculator
Calculate the series resistor an LED needs. Enter supply voltage, LED forward voltage and current to get the resistance, nearest E12 value and power.
Lens Magnification Calculator
Solve the thin lens equation 1/f = 1/do + 1/di and find magnification m = -di/do. Enter any two of focal length, object and image distance. Free tool.
Lens Maker's Equation Calculator
Find a lens focal length and power from its refractive index and surface radii using 1/f = (n-1)(1/R1 - 1/R2). Supports flat surfaces. Free and instant.
Lever Calculator
Solve the law of the lever, effort force times effort arm equals load force times load arm. Enter any three values to find the fourth and the advantage.
Light Travel Time Calculator
Calculate how long light takes to cross any distance. Enter kilometres, AU, light years, parsecs or miles to get seconds, minutes, hours, days and years.
Light Year Converter
Convert astronomical distances between light-years, AU, parsecs, kilometres, miles and metres. Fast, accurate unit conversion with worked examples. Free.
Luminosity Calculator
Calculate stellar luminosity with the Stefan-Boltzmann law, L = 4 pi r^2 sigma T^4. Enter a star's radius and temperature to get watts and solar units.
Magnification Calculator
Find total magnification for a microscope or telescope. Microscope multiplies objective by eyepiece; telescope divides objective focal length by eyepiece. Free.
Mass Percent Calculator
Calculate the mass percent of a solute by mass. Enter the solute mass plus the solvent mass or the total solution mass to get percent by mass instantly.
Mechanical Advantage Calculator
Calculate actual mechanical advantage from load and effort force, AMA = load / effort. Add the ideal mechanical advantage to find efficiency as a percent.
Mirror Equation Calculator
Solve the mirror equation 1/f = 1/do + 1/di with f = R/2. Find focal length, radius, image distance and magnification for concave and convex mirrors.
Molality Calculator
Calculate molality in moles of solute per kilogram of solvent. Enter moles, or a mass and molar mass, plus the solvent mass to get mol/kg instantly.
Molar Mass Calculator
Calculate the molar mass and molecular weight of any chemical formula. Get a full per element breakdown for compounds like H2O, NaCl, H2SO4 and hydrates.
Molarity Calculator
Calculate molarity in mol per litre and solve for moles, volume or concentration. Find moles from mass and molar mass, then get the missing value.
Mole Calculator
Convert between moles, mass and particles. Enter mass and molar mass, or moles, or a particle count, and get the rest using Avogadro's number.
Mole Fraction Calculator
Calculate the mole fraction of each component in a mixture. Enter the moles of every component and get each mole fraction, which together add up to 1.
Moment of Inertia Calculator
Find the moment of inertia for a cylinder, hoop, solid or hollow sphere, and a rod about its centre or end. Enter mass and a radius or length in SI units.
Momentum Calculator
Solve linear momentum p = m x v for mass, velocity or momentum, and find impulse from force and time. Impulse equals the change in momentum in SI units.
Newton's Law of Cooling Calculator
Find an object's temperature over time as it cools or warms toward ambient. Uses T = Ta + (T0 - Ta) e^(-k t). Enter ambient, initial, cooling constant and time.
Normality Calculator
Calculate normality from molarity and an equivalence factor, N = M times equivalents. Enter molarity to find normality, or normality to find molarity.
Ohm's Law Calculator
Solve Ohm's law online. Enter any two of voltage, current, resistance or power and get the other two, with the V, I, R and P formulas shown.
Op-Amp Gain Calculator
Calculate op-amp voltage gain and gain in dB for inverting and non-inverting configurations from the input and feedback resistors. Free EE design tool.
Orbital Period Calculator
Calculate orbital period from Kepler's third law, T = 2 pi sqrt(a cubed / GM). Enter the semi-major axis and central mass to get seconds, days and years.
Orbital Velocity Calculator
Calculate circular orbital velocity and period from the central mass and orbit radius, using v = sqrt(GM/r). Enter mass in kg and radius in km.
Parallax Distance Calculator
Calculate the distance to a star from its parallax angle. Distance in parsecs is 1 divided by the parallax in arcseconds, plus light years and AU.
Percent Composition Calculator
Calculate the percent composition by mass of each element in a chemical formula. Enter a compound like H2O or CO2 and get the molar mass breakdown.
Percent Yield Calculator
Calculate percent yield from actual and theoretical yield. Solve for actual or theoretical yield too, with a flag when the result exceeds 100 percent.
pH Calculator
Calculate pH, pOH and the H+ and OH- concentrations at 25C. Enter any one value and get the other three, with an acidic, neutral or basic verdict.
Planet Weight Calculator
Find your weight on other planets and the Moon. Enter your Earth weight in pounds or kilograms to see it scaled by each body surface gravity.
Power Calculator
Calculate power online. Solve mechanical power from work and time (P = W / t) or electrical power from voltage and current (P = V x I), in watts.
Power Factor Calculator
Calculate power factor, phase angle and reactive power from real and apparent power. Find pf, angle in degrees and VAR. Free electrical engineering tool.
Pressure Calculator
Solve pressure from force and area online. Enter any two of force, area or pressure and get the third, with newtons, pounds, square metres, psi and more.
Projectile Motion Calculator
Calculate projectile range, max height and time of flight from launch speed and angle. Supports custom gravity and launch height. Free physics calculator.
Pulley Calculator
Find pulley effort force and ideal mechanical advantage from the number of supporting ropes. Effort equals load divided by rope count for a block and tackle.
Pump Power Calculator
Calculate pump hydraulic power and shaft power from flow rate, head, fluid density and efficiency. Results shown in both watts and kilowatts.
Punnett Square Calculator
Build a monohybrid Punnett square from two parent genotypes. See the 2x2 cross grid, genotype ratios like 1:2:1 and the dominant to recessive split.
RC Time Constant Calculator
Find the RC time constant from resistance and capacitance, plus charge times and the cutoff frequency. Enter any two of R, C and tau to solve the third.
Redshift Calculator
Calculate cosmological redshift z from rest and observed wavelengths, then get the recession velocity and Hubble distance. Free online redshift tool.
Resistor Calculator
Add resistors in series or parallel and get the total resistance in ohms. Enter any number of values and the calculator shows the result with the formula.
Resistor Color Code Calculator
Decode 4-band and 5-band resistor color codes to ohms and tolerance, or encode a resistance into color bands. Free, with the values formatted clearly.
Resonant Frequency Calculator
Find the resonant frequency of an LC circuit with f = 1 / (2 pi sqrt(L C)). Enter inductance and capacitance to get the frequency and angular frequency.
Reynolds Number Calculator
Calculate the Reynolds number for pipe flow from velocity, diameter and viscosity, then see whether the flow is laminar, transitional or turbulent.
RMS Voltage Calculator
Convert between RMS, peak, peak-to-peak and average voltage for a sine wave. Enter one value to get the rest. Free electrical engineering calculator.
Rotational Kinetic Energy Calculator
Calculate rotational kinetic energy from moment of inertia and angular velocity using KE = 1/2 I omega squared. Get the spinning energy in joules.
RPM to Linear Velocity Calculator
Convert RPM and a wheel or pulley radius into surface speed in m/s and km/h. Enter radius or diameter to find linear velocity for CNC, belts and wheels.
Schwarzschild Radius Calculator
Calculate the Schwarzschild radius, the event horizon of a black hole, with r = 2GM/c^2. Enter a mass in kilograms or solar masses. Free online tool.
Serial Dilution Calculator
Work out a serial dilution tube by tube. Enter a stock concentration, a fold factor or transfer and diluent volumes, and read the value at each step.
Slope Grade Calculator
Convert slope between rise over run, percent grade, degrees and a 1:N ratio. Enter any one form and get the rest, plus the slope distance.
Snell's Law Calculator
Calculate the angle of refraction with Snell's law, n1 sin t1 = n2 sin t2. Find the refracted angle, the critical angle and total internal reflection. Free.
Soil Swell and Shrinkage Calculator
Convert soil volume between bank, loose and compacted states. Enter one volume with swell and shrinkage percent to get the other two in cubic yards.
Specific Heat Calculator
Solve Q = m c deltaT for heat, mass, specific heat or temperature change. Enter any three SI values to get the fourth, with common material hints.
Speed Distance Time Calculator
Work out speed, distance or time from the other two with speed = distance / time. Supports m/s, km/h and mph, plus metres, kilometres and miles.
Stadia Distance Calculator
Reduce a stadia reading to horizontal and vertical distance. Enter the rod intercept, vertical angle and the K and C constants to survey without a tape.
Surface Gravity Calculator
Calculate the surface gravity of any planet, moon or star with g = GM/r^2. Enter mass and radius, or pick a preset, and compare it to Earth gravity.
Telescope Focal Ratio Calculator
Calculate a telescope's focal ratio, Dawes resolving limit, max useful magnification, eyepiece magnification and exit pupil from focal length and aperture.
Telescope Magnification Calculator
Calculate telescope magnification from focal lengths, plus max useful power, exit pupil and focal ratio from your aperture. Free astronomy optics tool.
Thermal Expansion Calculator
Calculate linear thermal expansion with deltaL = alpha L deltaT. Enter the coefficient, length and temperature change for the change in length and final length.
Thin Lens Calculator
Solve the thin lens equation 1/f = 1/do + 1/di. Enter any two of focal length, object distance and image distance to find the third, plus magnification.
Three-Phase Power Calculator
Calculate real, apparent and reactive power of a three-phase system from line voltage, line current and power factor. Free electrical engineering tool.
Titration Calculator
Solve acid base titration problems with M1V1 = M2V2. Enter any three of acid and base molarity and volume, set proton counts, and find the missing value.
Torque Calculator
Calculate torque from force, lever arm and angle using T = F x r x sin(theta). Solve for torque, force or lever arm in newton-metres, 90 degrees by default.
Transformer Turns Ratio Calculator
Calculate transformer turns ratio from voltage or winding turns, then find the secondary voltage and secondary current for an ideal transformer. Free tool.
Voltage Divider Calculator
Calculate the output of a resistive voltage divider. Enter the input voltage and two resistors to get Vout, the current and the divider ratio instantly.
Voltage Drop Calculator
Calculate DC voltage drop along a wire run from current and resistance, or from resistance per meter and length. See volts dropped, percent and end voltage.
Wavelength Frequency Calculator
Convert wavelength to frequency and back using c = f x lambda. Enter a wavelength or frequency in metres, nm, Hz, MHz or GHz and get the photon energy too.
Wet Bulb Calculator
Calculate the wet bulb temperature from air temperature and relative humidity using the Stull 2011 formula. Get results in both Celsius and Fahrenheit.
Wheatstone Bridge Calculator
Find the unknown resistor of a balanced Wheatstone bridge from the three known resistors. Uses Rx = R2 R3 / R1. Free electrical engineering tool.
Wind Chill Calculator
Calculate the wind chill or feels like temperature from air temperature and wind speed using the NWS 2001 formula. Get results in both F and C.
Wire Gauge Calculator
Convert an AWG wire gauge to diameter, cross-sectional area and copper resistance per km. Higher gauge means thinner wire. Free electronics calculator.