Math

Triangular Number Calculator

nth triangular number, or the inverse index of a triangular value.

Free to use — no sign-up or login.

Result

This free Triangular Number Calculator covers nth triangular number, or the inverse index of a triangular value.

T_n = n(n+1)/2. Mode 0 computes T_n; mode 1 solves for n given T. Related math tools sit beside How it works, with no account required.

Using the Triangular Number Calculator

nth triangular number, or the inverse index of a triangular value. Typical inputs are n or T and Mode (0 = T_n, 1 = inverse). How it works beside the form states the identity the Triangular Number Calculator applies.

FAQ

How do I use the Triangular Number Calculator?

Open the Triangular Number Calculator, fill n or T and Mode (0 = T_n, 1 = inverse), and read the result. T_n = n(n+1)/2. Mode 0 computes T_n; mode 1 solves for n given T.

What formula does the Triangular Number Calculator use?

The Triangular Number Calculator uses the identity in How it works. In words: T_n = n(n+1)/2. Mode 0 computes T_n; mode 1 solves for n given T.