basic

Triangular Number Calculator

T_n = n(n+1)/2 — the sum 1 + 2 + … + n.

Compute the n-th triangular number T_n = n(n + 1) / 2 — the number of dots in a triangle with n dots on each side.

Daniel Oh By Daniel Oh
Published Last reviewed 1 min read

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Results

Enter values and click Calculate to see results.
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How to use this calculator

  1. Fill in the inputs above using the units you already have.
  2. Values update automatically as you type — no submit button needed.
  3. Hover any result row for the underlying formula and intermediate values.

Formula

T_n = n(n + 1) / 2

In depth

Compute the n-th triangular number T_n = n(n + 1) / 2 — the number of dots in a triangle with n dots on each side.