Arithmetic Series Sum Calculator
A free, browser-based calculator. Runs entirely in your browser — no sign up, nothing stored.
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Enter Values
Enter your values and press Calculate to see results.
How to use this calculator
- Enter the first term, common difference and number of terms.
- Read the last term and the sum.
How it works
Each term adds the common difference. Last term = a + (n−1)d; sum = n/2 × (2a + (n−1)d).
Worked example
a=2, d=3, n=10. Last term 29, sum 155.
Common mistakes
- Using a ratio instead of a difference — that's a geometric series.
- Off-by-one on n: it's the count of terms, not the last index.
Frequently asked questions
What's an arithmetic series?
A list of numbers where each step adds the same amount (the common difference), summed together.
Related tools
Tip: Enter any known values to calculate the remaining results.
All calculations run in your browser. Your inputs are never saved or transmitted.