Home › Calculators › Photon Energy Calculator
Photon Energy Calculator
Find the energy of a single photon from its wavelength or frequency with E = hc/λ = hf, or go backwards from the energy. You get the result in electronvolts and joules plus the momentum, wavenumber, molar energy and the part of the spectrum (with the color for visible light).
Last updated:
I know the
Enter your values to see the result.
Advertisement
Advertisement
How to use the Photon Energy Calculator
- Choose what you know: wavelength, frequency or energy.
- Enter the value and choose its unit.
- Read the photon energy in eV and the other results.
- See the spectrum band and, for visible light, the color.
- Copy the results or compare with the spectrum table.
Photon energy formulas
| Quantity | Formula | Example (λ = 532 nm) |
|---|---|---|
| Frequency | f = c / λ | 5.635 × 10¹⁴ Hz |
| Energy | E = h f = h c / λ | 3.734 × 10⁻¹⁹ J |
| Energy in eV | E (eV) ≈ 1239.84 / λ (nm) | 2.331 eV |
| Momentum | p = h / λ | 1.246 × 10⁻²⁷ kg·m/s |
| Wavenumber | ν̃ = 1 / λ | 18,797 cm⁻¹ |
| Molar energy | E × NA | 224.9 kJ/mol |
Visible light by color
| Color | Wavelength (nm) | Photon energy (eV) |
|---|---|---|
| Violet | 380 – 450 | 2.76 – 3.26 |
| Blue | 450 – 485 | 2.56 – 2.76 |
| Cyan | 485 – 500 | 2.48 – 2.56 |
| Green | 500 – 565 | 2.19 – 2.48 |
| Yellow | 565 – 590 | 2.10 – 2.19 |
| Orange | 590 – 625 | 1.98 – 2.10 |
| Red | 625 – 750 | 1.65 – 1.98 |
Band edges are conventional: different references draw the color and spectrum boundaries a few nanometres apart.
Frequently asked questions
How do you calculate the energy of a photon?
E = h f = h c / λ, where h = 6.62607015 × 10⁻³⁴ J·s is Planck's constant, c = 299,792,458 m/s, f is the frequency and λ the wavelength. Divide joules by 1.602176634 × 10⁻¹⁹ to get electronvolts.
Is there a quick formula from nm to eV?
Yes: E (eV) ≈ 1239.84 / λ (nm). A 532 nm green laser photon has about 2.33 eV, a 650 nm red one about 1.91 eV.
What is the momentum of a photon?
p = h / λ = E / c. Photons have no rest mass but carry momentum, which is the basis of radiation pressure and solar sails.
Why is UV light more harmful than visible light?
Each UV photon carries more energy (above about 3.3 eV), enough to break chemical bonds in DNA and other molecules. Increasing brightness at longer wavelengths increases the number of photons, not the energy of each one.
How much energy does a microwave or Wi-Fi photon have?
At 2.45 GHz a photon carries about 1.6 × 10⁻²⁴ J (10 µeV), roughly 200,000 times less than a visible photon, far too little to ionize atoms.
Is the color swatch exact?
No. Screens mix red, green and blue, so they cannot reproduce pure spectral colors. The swatch is a common approximation meant to show roughly what the wavelength looks like.
Are all the tools on FreeToolCabin tested for quality and accuracy?
Yes! Every tool on our site undergoes automated Q/A testing in real browser environments to ensure high precision, correct output, and zero errors. If you happen to spot a bug or have a suggestion, please contact us at [email protected] and our team will review it right away.
Related tools
Wavelength Frequency CalculatorConvert frequency to wavelength and back for light, radio or sound, with photon energy and band.E=mc2 CalculatorConvert mass to energy and back with E=mc², in joules, kWh, eV and tons of TNT.Thin Lens Equation CalculatorSolve 1/f = 1/do + 1/di for any value, with magnification, image type and a ray diagram.Resonant Frequency CalculatorLC resonant frequency f = 1/(2π√LC), or solve the inductance or capacitance you need.Speed Distance Time CalculatorSolve for speed, distance or travel time and get your arrival time.Half Life CalculatorSolve radioactive decay for amount left, half-life, time or initial amount, with a curve.Kinetic Energy CalculatorSolve KE = ½mv² and PE = mgh for energy, mass, speed or height, with unit conversions.Projectile Motion CalculatorRange, max height, flight time and impact speed of a projectile, with an animated trajectory.Free Fall CalculatorFall time and impact velocity from a height, or height from time or speed, with a chart and table.Meeting Cost CalculatorWork out what a meeting really costs from attendees and salaries, with a live cost ticker.Velocity CalculatorSolve v = d/t and a = Δv/t for any variable, plus a SUVAT solver for any three kinematics values.Torque CalculatorSolve τ = r·F·sin θ for torque, force, lever arm or angle, and convert torque to power at any rpm.Acceleration CalculatorAcceleration from velocity change and time, distance and time, or force and mass.Force CalculatorSolve F = ma for force, mass or acceleration, plus weight on every planet.Density CalculatorSolve density, mass or volume with unit conversion and a table of common material densities.Momentum CalculatorCalculate momentum (p = mv), mass, velocity, impulse and momentum change with unit conversion.Potential Energy CalculatorGravitational PE = mgh and spring PE = ½kx²: solve for energy, mass, height, k or stretch.Power CalculatorCalculate power from work and time, force and velocity, or volts and amps, in W, kW and hp.PPI CalculatorPixel density (PPI), dot pitch and retina viewing distance from resolution and screen size.Download Time CalculatorHow long a file takes to download at your internet speed, or the speed you need.Pressure CalculatorSolve P = F/A for pressure, force or area in Pa, kPa, bar, psi and atm.Work CalculatorSolve W = F·d·cos θ for work, force, distance or angle in J, kWh and ft-lb.Hooke's Law CalculatorSolve F = kx for spring force, spring constant or extension, plus stored spring energy.Centripetal Force CalculatorCentripetal force and acceleration from mass, radius and speed or RPM: F = mv²/r.Gravitational Force CalculatorNewton's law of gravitation F = Gm₁m₂/r² for any two masses, with planet presets.Speed of Sound CalculatorSpeed of sound from air temperature or medium, and distance from an echo or thunder delay.Doppler Effect CalculatorObserved frequency from source and observer speeds, or source speed from a pitch shift.Specific Heat CalculatorSolve Q = mcΔT for heat energy, mass, specific heat or temperature change, with materials.Decibel CalculatorAdd dB levels, convert power or voltage ratios to dB, and find sound level at a distance.Bernoulli Equation CalculatorSolve Bernoulli's equation for pressure, velocity or height, with pipe continuity and flow.Buoyancy CalculatorBuoyant force from fluid density, volume and gravity, with a float or sink check.Escape Velocity CalculatorEscape and orbital velocity for any planet, moon or custom mass and radius.Friction Force CalculatorStatic and kinetic friction from material presets, normal force or mass and incline angle.Inclined Plane CalculatorForces, acceleration and push force for a mass on a slope with friction.Light Travel Time CalculatorHow long light or radio takes to reach the Moon, Sun, Mars, Voyager 1 or any distance.Orbital Period CalculatorOrbital period from central mass and semi-major axis with Kepler's third law and presets.Pendulum Period CalculatorPendulum period and frequency from length and gravity, or length from period.Snell's Law CalculatorRefraction angle, critical angle and total internal reflection from n₁, n₂ and the angle.Inverse Square Law CalculatorFind light, sound or radiation intensity at a new distance, or the distance for a target.Lever CalculatorEffort force, load or arm length for class 1, 2 and 3 levers, with mechanical advantage.Lightning Distance CalculatorTap at the flash and again at the thunder to see how far away lightning struck, in miles and km.Magnetic Declination CalculatorFind magnetic declination, inclination and field strength for any place and date (WMM2025).Map Radius ToolDraw circles of any radius around points on a map, with multiple rings and a share link.MTBF CalculatorMTBF, failure rate, availability and mission reliability from operating hours and failures.Pipe Pressure Drop CalculatorDarcy-Weisbach pressure drop and head loss with Reynolds number and Colebrook friction factor.Refrigerant PT ChartPressure-temperature chart for R-410A, R-32, R-454B, R-22, R-134a, R-404A and more.Reynolds Number CalculatorReynolds number and laminar, transitional or turbulent regime for pipes, ducts, plates and spheres.RMS Voltage CalculatorConvert peak, peak-to-peak, RMS and average voltage for sine, square and triangle waves.Spring Rate CalculatorCompression spring rate from wire size, coil diameter, coils and material, plus solid height.Standard Atmosphere (ISA) CalculatorISA 1976 temperature, pressure, density, speed of sound and viscosity at any altitude to 86 km.Steam Table CalculatorSaturated and superheated steam properties: enthalpy, entropy, volume and quality (IAPWS-IF97).Superheat and Subcooling CalculatorFind superheat, subcooling and target values from gauge pressures and line temperatures.Thermal Expansion CalculatorLinear, area or volume expansion from size, temperature change and material coefficient.Top of Descent CalculatorWhen to start descending: distance and time to top of descent, required fpm, 3-degree rule.True Airspeed CalculatorTrue airspeed, Mach number and density altitude from IAS/CAS, pressure altitude and OAT.Valve Cv CalculatorSize a valve: required Cv or Kv for liquid, gas or steam, or flow and pressure drop from Cv.Water Heating Time CalculatorHow long to heat water: time, energy and cost from volume, temperatures and heater power.Wave Speed CalculatorSolve v = f × λ, find wave speed from distance and time, or from string tension and density.Speeds and Feeds CalculatorSpindle RPM and feed rate (mm/min, in/min) from tool size, flutes, surface speed and chip load.Terminal Velocity CalculatorTerminal velocity and time to 95% from mass, drag coefficient, area and air density.Time Dilation CalculatorLorentz factor, dilated time and length contraction from speed and proper time.Displacement CalculatorDisplacement from velocity and time, s = ut + ½at², or start and end coordinates, with steps.Kinematics Calculator (SUVAT)Enter any 3 of s, u, v, a and t to solve the other 2 with the SUVAT equations shown.3D Printer Filament Length CalculatorFilament weight to length and back for PLA, PETG, ABS and more, plus spool remaining.Fuel Injector Size CalculatorInjector size in lb/hr and cc/min from target horsepower, BSFC, cylinders, duty cycle and fuel.Hull Speed CalculatorTheoretical displacement hull speed from waterline length, in knots, mph and km/h.OEE CalculatorOverall equipment effectiveness from time, ideal cycle time and counts: A × P × Q.Scuba Air Consumption CalculatorSAC and RMV from a logged dive, then gas needed, turn pressure and bottom time for the next.