Arithmetic Series Sum Calculator
Calculate the sum of an arithmetic sequence from its first term, common difference and number of terms, free in your browser.
Enter Values
Minimum 1
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
How do I sum an arithmetic series?
Sum = n ÷ 2 × (first term + last term), where n is the number of terms — pairing terms from the ends.
What's the difference between a sequence and a series?
A sequence is the list of terms; a series is their sum.
What's an arithmetic series?
A list of numbers where each step adds the same amount (the common difference), summed together.
Related tools
- Geometric Series Sum Calculator
- Arithmetic Sequence Calculator
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- Fibonacci Calculator
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- Average (Mean) Calculator
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Cite this tool
Zerdly. (2026). Arithmetic Series Sum Calculator. Retrieved from https://www.zerdly.com/tools/arithmetic-series-sum-calculator/
Tip: Enter any known values to calculate the remaining results.
Designed to run locally in your browser. Tool inputs are not intentionally stored by Zerdly unless stated otherwise.