Enter any two values (photon energy E, frequency f, or Planck’s constant h) to solve the photon relation E = h·f. Note: Planck’s constant is a fixed physical constant in SI; the calculator can also be used to estimate h from measured photon energy and frequency (for example, in photoelectric-effect experiments).

Planck’s Constant Calculator

Uses photon relations: E = h·f, E = h·c/λ, and f = c/λ (in vacuum). In SI, h is exactly 6.62607015×10⁻³⁴ J·s.

Enter any 2 values to calculate the missing variable (for photon energy and frequency). To estimate h, leave the Planck’s Constant field blank.

Tip: Reset restores h to 6.62607015×10⁻³⁴ J·s.

Related Calculators

Planck’s Constant Formula

h = E / f

Variables (for photons / electromagnetic radiation):

  • h is Planck’s constant (J·s)
  • E is the photon energy (J)
  • f is the frequency (Hz)

Solving E = h·f for h gives h = E / f. In SI units, Planck’s constant is defined to be exactly 6.62607015×10⁻³⁴ J·s, so this calculation is mainly used to estimate h from experimental measurements of photon energy and frequency.

How to Estimate Planck’s Constant (from E and f)

The following steps outline how to estimate Planck’s constant from photon measurements.

  1. First, determine the photon energy E (for example, from an experiment such as the photoelectric effect). 
  2. Next, determine the frequency f. 
  3. Next, gather the formula from above: h = E / f. 
  4. Finally, calculate the estimate of Planck’s constant. 
  5. After inserting the variables and calculating the result, compare your estimate to the accepted value (6.62607015×10⁻³⁴ J·s) using the calculator above.

Example Problem : 

Use the following variables as an example problem to test your knowledge (photon case, E = h·f).

energy = 3.313035075×10⁻¹⁹ J

frequency = 5.00×10¹⁴ Hz (500 THz)

Frequently Asked Questions (FAQ)

What is Planck’s Constant used for in physics?

Planck’s Constant is a fundamental constant used to describe the sizes of quanta in quantum mechanics. It plays a crucial role in the quantum theory of electromagnetic radiation, the photoelectric effect, and blackbody radiation, among other phenomena.

How does the value of Planck’s Constant impact the physical world?

The value of Planck’s Constant determines the scale at which quantum effects become significant. If it were significantly larger, everyday movements might involve noticeable quantum effects, while if it were smaller, quantum mechanics might only be observable at much smaller scales.

Can Planck’s Constant change over time?

Current scientific consensus holds that Planck’s Constant is a fixed quantity and does not change over time. However, ongoing research in the constants of nature continues to test this and other fundamental assumptions.

Why is Planck’s Constant considered a fundamental constant?

Planck’s Constant is considered fundamental because it sets the scale of quantized action in quantum mechanics, linking the energy a photon carries with the frequency of its electromagnetic wave through E = h·f. Its universality and constant value make it a cornerstone of quantum physics.