Arithmetic Sequence Calculator • nth term • sum • list • inverse

Arithmetic Sequence Calculator Built for Students, Teachers, and Fast Problem Solving

Use this premium arithmetic sequence calculator to find the nth term, generate a full arithmetic sequence list, calculate the sum of an arithmetic series, and solve for the term position from a target value. The tool updates instantly, shows the exact formula used, and breaks the sequence down into a clean table so you can verify every step.

4 solve modesnth term, sum, list, inverse
Instant tableSee term number and value side by side
Works with negativesIncreasing and decreasing sequences supported

Why this page feels premium

Live calculationEvery result updates while you type, so the flow feels fast on mobile and desktop.
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Formula-awareYou see the exact arithmetic sequence formula and the substituted values, not just a final answer.
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Learning supportExamples, definitions, and FAQs make the page useful for homework, revision, and exam prep.

What you can solve here

nth termFind any term when you know the first term, difference, and position.
Σ
Series sumCalculate the total of the first n terms in one step.
n?
Inverse modeWork backward from a target term to find its position in the arithmetic sequence.

Arithmetic Sequence Solver

Enter your first term, common difference, and other values below. This arithmetic progression calculator handles positive, negative, and decimal inputs, and it automatically explains the sequence rule.

This is the first value in the sequence.
Use a negative number for decreasing arithmetic sequences.
Choose the position you want to analyze.
The calculator uses this value for the list preview and the working table.
Rule: add 4 each time, starting from 3.
Sequence preview
This preview helps you verify the pattern visually before you use the nth-term or sum result.

Results

10th term 39 Using aₙ = a₁ + (n - 1)d
Sum of first n terms 210 Arithmetic series total up to n
Sequence type Increasing Constant step size = 4
Average of first and nth term 21 Useful in the series sum formula

Exact formula used

aₙ = 3 + (10 - 1) × 4 = 39

Step-by-step explanation

Take the first term 3, move forward 9 gaps, and add the common difference 4 for each gap. That gives 3 + 36 = 39.

n Formula Value

Arithmetic sequence formula

aₙ = a₁ + (n - 1)d

Use this formula to find any term in an arithmetic sequence. The first term is a₁, the common difference is d, and n is the term number.

Arithmetic series sum formula

Sₙ = n / 2 × [2a₁ + (n - 1)d]

Use this when you want the total of the first n terms and you know the first term, common difference, and term count.

Inverse formula to find n

n = ((aₙ - a₁) / d) + 1

This is useful when you know the target term value and want to know where it appears in the arithmetic progression.

How to use

Enter the first term and the common difference, choose a mode, and type the term number or target term. The page updates in real time and instantly shows the arithmetic sequence answer.

Best for students

Use it as an arithmetic progression calculator during homework, revision sessions, or when checking worksheet solutions before submission.

Best for teachers

Generate sequence tables quickly for examples, assessments, class slides, and explanation notes without building the list manually.

Best for test prep

When speed matters, you can switch between nth-term, sum, and inverse mode without leaving the page, which is ideal for exam practice.

Worked example

Suppose the first term is 7, the common difference is 5, and you want the 12th term. The formula becomes a₁₂ = 7 + (12 - 1) × 5. That is 7 + 55 = 62. If you also want the sum of the first 12 terms, apply S₁₂ = 12 / 2 × [2 × 7 + (12 - 1) × 5] = 6 × (14 + 55) = 414.

Benefits

  • Find arithmetic sequence terms instantly without writing long manual steps.
  • Check arithmetic series totals for quiz practice and assignment work.
  • Generate list previews to verify patterns before trusting the result.
  • Solve backward from a known term value using inverse mode.

When to use this calculator

An arithmetic sequence calculator is helpful in algebra classes, aptitude practice, spreadsheet planning, budgeting intervals, installment patterns, and any situation where values change by a constant amount each step.

Arithmetic Sequence Calculator Guide

An arithmetic sequence calculator is one of the most useful algebra tools for anyone who works with number patterns. In an arithmetic sequence, each term changes by the same fixed amount. That constant change is called the common difference. Because the step stays the same from one term to the next, arithmetic sequences are easier to predict than many other number patterns. A strong arithmetic progression calculator takes that rule and turns it into instant outputs for the nth term, the arithmetic series sum, and the full list of terms.

This page is designed for people who want more than a tiny formula box. Many visitors search for an arithmetic sequence calculator because they need fast help with homework, but the best tool also helps them understand the pattern. That is why this calculator shows the sequence preview, the substituted formula, and the result table at the same time. You can use it as an nth term calculator when you already know the first term and common difference. You can also use it as an arithmetic series calculator when you need the total of the first n terms. If you know a term value and want to solve for the position, inverse mode handles that too.

The most common formula in any arithmetic sequence problem is aₙ = a₁ + (n - 1)d. This equation tells you how to move from the first term to any later term. If d is positive, the sequence increases. If d is negative, the sequence decreases. If d is zero, every term is the same. Students often lose marks by mixing up the term number and the common difference, which is why a live arithmetic sequence formula calculator is useful. You see the exact values substituted into the formula before you trust the answer.

Another high-demand use case is the arithmetic series sum formula. Instead of adding each term one by one, the calculator uses Sₙ = n / 2 × [2a₁ + (n - 1)d]. This is much faster when n is large. Imagine a sequence starting at 15 and increasing by 3. If you need the sum of the first 100 terms, manual addition is slow and error-prone. The series formula solves the problem in seconds. That is why people often search for terms such as arithmetic series calculator, sum of arithmetic sequence calculator, and arithmetic progression sum calculator.

The page is also helpful for real-life patterns. Savings targets that rise by a constant amount every month, stair designs with equal incremental changes, installment plans, repeated scheduling blocks, and fixed-rate inventory growth can all be modeled by arithmetic progressions. When you use an arithmetic sequence calculator for these scenarios, the formula becomes practical rather than theoretical. You can test a pattern, adjust the common difference, and see the result immediately.

For learning, the sequence list preview matters a lot. If the first term is 2 and the common difference is 6, the preview should read 2, 8, 14, 20, and so on. A calculator that only prints a single answer does not help you confirm the pattern. Here, you get a working list and a term-by-term table. This makes the tool useful not only as a number sequence calculator but also as a pattern-checking tool. Students can compare their handwritten work with the on-page list and spot mistakes quickly.

Inverse solving is another premium feature. Sometimes the question is not “What is the 20th term?” but “In which term does 83 appear?” In that case, you rearrange the arithmetic sequence formula and solve for n. This page does that automatically. If the result is a whole number, the target value belongs to the sequence. If the result is not an integer, the chosen value does not appear as an exact term. That kind of feedback is extremely useful for checking whether a number fits the progression rule.

Searchers often look for an arithmetic sequence calculator with steps because many online tools provide only a final output. This page is intentionally built to be more transparent. You can read the formula line, the verbal explanation, the sequence type, and the average of the first and nth term. Those elements help users understand why the answer is correct. This is especially helpful for classwork, exam revision, and tutoring support where showing the reasoning is just as important as getting the final number.

If you are comparing tools, a good arithmetic progression calculator should be fast on mobile, easy to read, and flexible enough to handle negative differences, decimals, and larger term counts. It should also support both quick checking and deeper study. That is the direction of this page. Whether you are searching for an arithmetic sequence calculator online, an AP sequence calculator, a common difference calculator, or a sum of terms calculator, this tool combines those functions into one cleaner workflow.

To get the best results, always start by identifying the first term correctly. Then confirm the common difference by subtracting consecutive terms. Once those two values are correct, most arithmetic sequence problems become straightforward. The calculator then acts as a fast verification system. If your pattern is not arithmetic, the outputs may not align with your expected values, which is a useful warning sign in itself.

FastCalc built this page to feel stronger than a simple worksheet helper. It is meant to be a reliable arithmetic sequence calculator for students, teachers, and anyone who wants instant math answers without sacrificing clarity. Use the nth-term mode for direct pattern questions, use the sum mode for arithmetic series totals, use the list mode when you need a clean table, and use inverse mode when you want to work backward from a target value. That combination makes this one of the most complete arithmetic sequence and series tools on the page.

Frequently asked questions

What is an arithmetic sequence calculator?

An arithmetic sequence calculator is an online math tool that works with number patterns where each term changes by a constant amount. It can find the nth term, build the term list, and calculate the sum of the first n terms.

What is the difference between an arithmetic sequence and an arithmetic series?

An arithmetic sequence is the ordered list of terms. An arithmetic series is the sum of those terms. This page handles both, so you can switch between term-level and total-level calculations easily.

Can this calculator handle decimals and negative differences?

Yes. You can enter decimal values and negative common differences. The calculator will still generate the correct arithmetic progression rule and outputs.

How do I know if a value belongs to the sequence?

Use inverse mode. Enter the first term, common difference, and target value. If the resulting term number is a whole number greater than zero, the target value appears in the sequence exactly.