Arithmetic Sequence Calculator

Q: What is an arithmetic sequence?

An arithmetic sequence (or arithmetic progression) is a sequence of numbers where each term after the first is obtained by adding a constant value called the common difference (d) to the previous term. For example, 2, 5, 8, 11, 14 is an arithmetic sequence with a common difference of 3.

Q: How do you find the nth term of an arithmetic sequence?

Use the formula aₙ = a₁ + (n-1)d, where a₁ is the first term, n is the position, and d is the common difference. For example, to find the 10th term of sequence 3, 7, 11, ...: a₁₀ = 3 + (10-1)×4 = 3 + 36 = 39.

Q: How do you calculate the sum of an arithmetic sequence?

Use Sₙ = n(a₁ + aₙ)/2 or Sₙ = n[2a₁ + (n-1)d]/2. The first formula requires knowing the first and last terms; the second only needs the first term and common difference.

Q: What is the common difference?

The common difference (d) is the constant value added to each term to get the next term. Calculate it by subtracting any term from the next: d = a₂ - a₁. It can be positive, negative, or zero.

Q: Can arithmetic sequences have negative numbers?

Yes. The first term can be negative, the common difference can be negative (decreasing sequence), or both. Example: -10, -7, -4, -1, 2 has first term -10 and common difference 3.

Calculate the nth term and sum of arithmetic sequences with step-by-step solutions, interactive visualizations, and high-precision results up to 1000 decimal places.

Free to useNo sign-up requiredUpdated Jan 2026

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Quick Examples

📐 Basic (2,5,8...) 📉 Decreasing 🔬 Decimals ➖ Negative Start

First Term (a₁)

Common Difference (d)

Find Term Number (n)

Precision

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About Arithmetic Sequence Calculator

Welcome to the Arithmetic Sequence Calculator, a professional-grade tool for computing the nth term and sum of arithmetic sequences with high precision. Whether you're a student learning sequences, a teacher preparing materials, or a professional working with mathematical series, this calculator provides accurate results with step-by-step explanations and visual representations.

What is an Arithmetic Sequence?

An arithmetic sequence (also called an arithmetic progression or AP) is a sequence of numbers where each term after the first is obtained by adding a constant value called the common difference to the preceding term. This creates a linear pattern that increases, decreases, or remains constant depending on the common difference.

For example, the sequence 2, 5, 8, 11, 14, ... is an arithmetic sequence with:

First term (a₁) = 2
Common difference (d) = 3

Key Formulas

The nth Term Formula

To find any term in an arithmetic sequence, use this formula:

nth Term of Arithmetic Sequence

$$a_n = a_1 + (n - 1)d$$

Where:

aₙ = the nth term you want to find
a₁ = the first term of the sequence
n = the position of the term
d = the common difference

Sum of Arithmetic Sequence

To calculate the sum of the first n terms, use one of these equivalent formulas:

Sum of First n Terms

$$S_n = \frac{n(a_1 + a_n)}{2} = \frac{n[2a_1 + (n-1)d]}{2}$$

The first form is useful when you know both the first and last terms. The second form is useful when you only know the first term and common difference.

How to Use This Calculator

Enter the first term (a₁): Input the starting value of your sequence. This can be any real number, including decimals and negative values.
Enter the common difference (d): Input the constant value added between terms. Positive values create increasing sequences; negative values create decreasing sequences.
Enter n: Specify which term you want to find and how many terms to sum.
Select precision: Choose the number of decimal places for calculations (10 to 1000).
Calculate: Click the button to see the nth term, sum, sequence preview, visualization, and step-by-step solution.

Understanding Your Results

Sequence Preview: Shows the first several terms to help you visualize the pattern.
The nth Term (aₙ): The specific term at position n in the sequence.
Sum (Sₙ): The total when you add the first n terms together.
Visualization: A bar chart showing the term values graphically.
Step-by-Step Proof: Complete formula breakdown showing exactly how the results were calculated.

Types of Arithmetic Sequences

Type	Common Difference	Example	Pattern
Increasing	d > 0	3, 7, 11, 15, 19	Terms grow larger
Decreasing	d < 0	20, 15, 10, 5, 0	Terms grow smaller
Constant	d = 0	5, 5, 5, 5, 5	All terms equal

Real-World Applications

Finance & Economics

Simple Interest: Interest grows by a fixed amount each period
Linear Depreciation: Asset value decreases by a constant amount annually
Salary Increments: Fixed annual raises create an arithmetic sequence

Science & Engineering

Uniformly Accelerated Motion: Distance traveled in equal time intervals
Temperature Scales: Converting between Fahrenheit and Celsius
Stacking Problems: Number of items in stacked arrangements

Everyday Examples

Numbered seats in a theater row
Stairs with equal height steps
Clock times at regular intervals
Page numbers in a book

Arithmetic vs Geometric Sequences

Property	Arithmetic Sequence	Geometric Sequence
Pattern	Add constant difference	Multiply by constant ratio
nth Term	aₙ = a₁ + (n-1)d	aₙ = a₁ × rⁿ⁻¹
Graph Shape	Linear (straight line)	Exponential (curve)
Example	2, 5, 8, 11, 14	2, 6, 18, 54, 162

Frequently Asked Questions

What is an arithmetic sequence?

An arithmetic sequence (or arithmetic progression) is a sequence of numbers where each term after the first is obtained by adding a constant value called the common difference (d) to the previous term. For example, 2, 5, 8, 11, 14 is an arithmetic sequence with a common difference of 3.

How do you find the nth term of an arithmetic sequence?