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Heisenberg Uncertainty Principle Calculator

Compute the minimum uncertainty allowed by quantum mechanics with Δx·Δp ≥ ħ/2 — enter the position uncertainty to get the minimum momentum uncertainty, or solve the other way.

 

Formula

$$ \Delta x\,\Delta p \ge \dfrac{\hbar}{2} \qquad \Delta p_{min}=\dfrac{\hbar}{2\,\Delta x} \qquad \Delta x_{min}=\dfrac{\hbar}{2\,\Delta p} $$
ħ = 1.0546×10⁻³⁴ J·s (reduced Planck constant)

Worked example

Confining an electron to an atom-sized Δx = 1×10⁻¹⁰ m forces a momentum uncertainty of at least \( \Delta p = \hbar/(2\Delta x) = (1.0546\times10^{-34})/(2\times10^{-10}) \approx 5.3\times10^{-25}\ \text{kg·m/s} \).

How it works

Heisenberg's uncertainty principle sets a fundamental limit: the more precisely a particle's position is known, the less precisely its momentum can be, and vice versa. The product of the uncertainties can never fall below ħ/2: Δx·Δp ≥ ħ/2.

This is not a measurement flaw but a property of quantum systems. The calculator returns the minimum uncertainty in one quantity given the other, using the reduced Planck constant ħ = 1.0546×10⁻³⁴ J·s.

For the underlying physics, read our explanation of quantum tunneling and the uncertainty principle.

Frequently asked questions

What is the Heisenberg uncertainty principle?

It states that the position and momentum of a particle cannot both be known exactly: Δx·Δp ≥ ħ/2. Reducing the uncertainty in one increases it in the other.

What is the value of ħ (h-bar)?

The reduced Planck constant ħ = h/2π ≈ 1.0546×10⁻³⁴ J·s. It sets the scale of the smallest possible uncertainty product.

Does the uncertainty principle come from imperfect instruments?

No. It is a fundamental property of quantum systems, not a limitation of measurement tools. Even with perfect instruments the product Δx·Δp cannot be less than ħ/2.

Why don't we notice it in everyday life?

Because ħ is extraordinarily small. For macroscopic objects the required uncertainties are far too tiny to detect; the principle only matters at atomic and subatomic scales.

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