Arithmetic Sequence Calculator

1. Select First term & common difference or Two known terms.
2. Enter the values for that mode, then enter a positive whole number in Which term to solve for (n).
3. Select Calculate to show the term, sum, formula, and calculation steps.
4. Select Copy result or Download result (.txt) to keep the displayed text.

Calculate an nth term from a first term and difference

Select First term & common difference when the starting value and repeated change are known. Common difference can be negative, zero, or a decimal. In Which term to solve for (n), use 1 for the first term, 2 for the second, and so on.

First term = 3
Common difference = 4
Which term to solve for (n) = 5

a_5 = 19
S_5 = 55

Find an arithmetic sequence from two known terms

Select Two known terms when the values and positions are available for two entries. Their positions must be different positive whole numbers. For example, term 2 = 7 and term 5 = 19 produces a common difference of 4 and a first term of 3. The calculator then uses those values for the requested term and sum.

Review the nth term and arithmetic sequence sum

Result shows the first term, common difference, requested term, and sum through n. Formula & steps lists each substitution. First terms of the sequence prints the preview. Editing an input or switching modes hides the previous result.

Copy result puts the displayed text on the clipboard when the copy action succeeds. Download result (.txt) saves the same text as a file. Reset clears the fields and hides the result. The calculation runs in the browser, and the page makes no request with the values entered here.

Arithmetic sequence calculator input rules

• Enter values as plain decimal text, with an optional leading minus sign. The parser rejects exponent notation and a leading plus sign.
• Term positions must be positive whole numbers, and the two known-term positions must be different.
• n and known-term positions cannot exceed 1,000,000,000.
• When n is greater than 50, the preview lists the first 50 terms and marks how many terms the full sequence contains.
• Enter consistent units as plain numbers when needed. The calculator leaves units unchanged and unlabeled.

Where an nth term calculation comes up

For a sequence exercise, enter the first term, its difference, and the requested position, then compare the displayed substitutions with the written work.

For repeated amounts in dollars, meters, or item counts, enter each quantity as a number using the same unit throughout. Read the requested term or the sum through it.

When two numbered observations are available, choose Two known terms, enter each position and value, and calculate the starting term before checking another position.

When another math calculator fits better

Use Math Calculators when you need a different kind of calculation. Choose Geometric Sequence Calculator for a constant ratio or an infinite sum. Choose Sequence Calculator when you need arithmetic and geometric sequence modes or missing-value calculations. For equations rather than sequences, use Algebra Calculator.

Frequently asked questions