Calculate the n-th triangular number using the arithmetic-series formula.
Last updated: June 2026 | By Patchworkr Team
Enter a whole number.
Triangular numbers are the sums of the first n non-negative integers.
1. Enter the term number n.
2. Read the live triangular number.
3. Compare it to the running sum 1 + 2 + ... + n if you want a quick check.
For n = 6:
T6 = 6 * 7 / 2 = 21
No. Triangular numbers are defined here for whole numbers only.
Yes. T0 = 0.
The calculator rejects negative values.
Very large integers may exceed safe integer precision, so the tool stays within safe whole numbers.
Related Tools