How it works
Find the nth term and sum of an arithmetic sequence, where each term changes by the same fixed amount.
aₙ = a₁+(n−1)d; Sₙ = n(a₁+aₙ)/2
Worked example
Show example inputs and result
First term: 3 · Common difference: 2 · Number of terms: 10.
- Nth term
- 21
- Sum
- 120
Questions and answers
Why are some results rounded?
Results display up to 8 decimal places. Calculations use the unrounded values; very small values use scientific notation. JavaScript floating-point arithmetic can introduce tiny rounding differences.
Are my inputs sent to a server?
The calculator processes inputs in your browser. Its code does not send your values to a server.
Method reviewed: October 8, 2026 · Methods & accuracy