Formula
Principal square root = √x, where the result r is the non-negative number satisfying r × r = x. Square check = result².
Square Root Calculator
Find the principal square root of a number, its square check and an optional rounded classroom or worksheet result.
Worked example
For x = 144, the principal square root is 12 because 12 × 12 = 144. For x = 2, the root is about 1.4142; squaring that rounded value gives about 2.0000, with small differences caused by rounding.
Professional note
Master’s Tip: when this result will be used in geometry, keep at least two extra decimal places during working and round only the final answer. Early rounding can move a length, diagonal or standard-deviation result enough to matter.
Regional and unit assumptions
Standard or basis: ordinary real-number arithmetic using the principal non-negative square root. The page does not simplify radical notation or handle complex-number roots.
Assumptions and limitations
- The public calculator accepts non-negative real numbers only.
- The displayed result is rounded to the selected number of decimal places, but the square-back check uses the calculated value before display rounding.
- Perfect squares give whole-number roots; non-perfect squares usually need decimal or radical notation.
- Negative-number square roots require complex numbers and are outside this basic real-number calculator.
Methodology & Accuracy
How this calculator is checked
CalculationTime pages are built around visible arithmetic: the formula, assumptions, worked example and practical limitations are shown so the result can be checked rather than simply trusted.
Formula used
Principal square root = √x, where the result r is the non-negative number satisfying r × r = x. Square check = result².
Standard or basis
Standard or basis: ordinary real-number arithmetic using the principal non-negative square root. The page does not simplify radical notation or handle complex-number roots.
Where a calculator follows a named legal, trade or industry standard, that standard is cited visibly. Otherwise the page uses transparent general arithmetic and states its limits.Master's Tip
Master’s Tip: when this result will be used in geometry, keep at least two extra decimal places during working and round only the final answer. Early rounding can move a length, diagonal or standard-deviation result enough to matter.
Related calculators
Questions
What is a square root?
A square root of a number is a value that gives the original number when multiplied by itself. For example, 12 is a square root of 144 because 12 × 12 = 144.
Why does the calculator show the principal square root?
For non-negative real numbers, the principal square root is the non-negative answer normally meant by the √ symbol. Although 12 and −12 both square to 144, √144 is written as 12.
Can I calculate the square root of a negative number here?
No. Negative square roots require complex numbers, such as i notation. This page is a basic real-number calculator for non-negative inputs.
Why is my square root a long decimal?
Many numbers are not perfect squares, so their square roots do not end as neat decimals. The decimal places field controls how much of the rounded result is shown.
How can I check a square root answer?
Multiply the result by itself. If the square-back check is close to the original number, the square root is correct within the displayed rounding.
Calculation note
Square roots appear anywhere a squared quantity needs to become a length or original scale again: geometry, measurement, statistics, engineering and school algebra. A transparent calculator should show both the root and the square-back check so the answer can be audited.
A square root reverses squaring
Squaring turns a side length into an area-style quantity: 12 squared is 144. A square root moves the other way by finding the non-negative value that squares back to the number entered.
Perfect squares and decimal roots behave differently
Numbers such as 4, 9, 16, 25 and 144 are perfect squares because their principal square roots are whole numbers. Many everyday measurements are not perfect squares, so the root is a rounded decimal and the rounding should be visible.
The printable check is the safeguard
The report keeps the input, displayed root, square-back check, formula and rounding setting together. That makes the page useful as a homework worksheet, geometry note, statistics check or measurement record rather than just a single loose answer.
Sources and further readingEncyclopaedia Britannica: Square rootOpenStax Algebra and Trigonometry: Radicals and rational exponents