Cubic Cell Calculator
Choose a cubic crystal structure and enter the lattice parameter (edge length). The calculator returns the unit-cell volume, the number of atoms per conventional cell, the idealized hard-sphere atomic radius, and, if you supply a molar mass, the theoretical density.
Last updated: September 26, 2026
Frequently asked questions
What is a cubic unit cell?
It's the smallest repeating cubic box that, stacked in three dimensions, builds up an idealized crystal lattice. Simple cubic, body-centered cubic, and face-centered cubic differ in how many atoms occupy that box.
How many atoms are in each structure?
Simple cubic has 1 atom per conventional cell (corner atoms shared among 8 cells), body-centered cubic has 2 (corners plus one center atom), and face-centered cubic has 4 (corners plus six face-centered atoms, each shared between 2 cells).
Is the lattice parameter the same as the atomic radius?
No. The lattice parameter a is the edge length of the unit cell. The atomic radius is derived from it using a geometric relationship that depends on the structure, since atoms touch along different directions in each lattice type.
How accurate is the density calculation?
It assumes a perfect, defect-free lattice of identical hard spheres, using the theoretical relationship ρ = nM/(NA·a³). Real materials can have vacancies, impurities, or different actual packing, so measured density can differ slightly from this idealized value.
Can I use this for any crystal structure?
Only for the three cubic structures listed: simple cubic, body-centered cubic, and face-centered cubic. Hexagonal, tetragonal, and other non-cubic lattices need different geometric relationships not covered here.
How does this relate to Avogadro's Number?
The density formula uses the Avogadro constant to convert from atoms per cell and molar mass into a mass per unit volume. See the Avogadro's Number Calculator for mole-to-particle conversions on their own.