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Square diagonal calculator

Compute the diagonal and area of a square from its side length.

Related tools

All Geometry tools →
Rectangle diagonal calculatorCompute the diagonal, area and perimeter of a rectangle.Square calculatorAll four measures of a square from any one. Give the side, the area, the perimeter or the diagonal and it returns the rest — side s, area s², perimeter 4s and diagonal s√2 — instantly.Magic square generatorGenerate a magic square of any order from 3 to 20 — a grid of the numbers 1…N² where every row, column and diagonal adds to the same magic constant. It picks the right construction automatically: the Siamese method for odd orders, diagonal complements for multiples of four, and the Strachey method otherwise.Equilateral triangle calculatorCompute the area, height and perimeter of an equilateral triangle from its side.Hexagon area calculatorCompute the area of a regular hexagon from its side length.Pentagon area calculatorCompute the area of a regular pentagon from its side length.Regular polygon area calculatorCompute the area of a regular polygon from its number of sides and side length.Regular polygon perimeter calculatorCompute the perimeter of a regular polygon from its number of sides and side length.

Enter Side length and the Square diagonal calculator works out Diagonal, Area straight away. For instance, with Side length = 5 it returns Diagonal = 7.071 and Area = 25.

How to use it

  1. Enter your values: Side length.
  2. Read the result instantly: Diagonal, Area.

Frequently asked questions

How does the Square diagonal calculator work?

It takes Side length and derives Diagonal and Area from them. The calculation is live as you type, so the result updates on every change.

Which values does the calculator ask for?

A single value: Side length. Nothing else is required — no account, no file upload.

What does a typical calculation look like?

With Side length = 5, the calculator returns Diagonal = 7.071 and Area = 25. Those figures come from running this exact tool, so you can reproduce them by entering the same values.

How much does the result change with different inputs?

It moves a lot. Using Side length = 10 instead, Diagonal goes from 7.071 to 14.142 — which is why it is worth testing a few scenarios rather than trusting a single figure.

What does it give for smaller values?

Scaled down to Side length = 3, Diagonal comes out at 4.243. The relationship is worth checking at both ends before you rely on a single result.

When would I actually use this?

Homework and site work alike: how much paint a wall takes, how much water a tank holds, whether a corner is square — and, on the coordinate side, the slope between two points, the distance across a plan, the midpoint of a span.

What is the most common mistake?

Mixing units inside one shape. Entering a length in centimetres and a width in metres gives an area wrong by a factor of a hundred, and the result looks perfectly plausible.

What is the difference between the Square diagonal calculator and the Rectangle diagonal calculator?

Both return Diagonal and Area. What differs is what they ask for: this one wants Side length, the Rectangle diagonal calculator wants Width and Height. Use whichever matches the numbers you already have.

Is there a tool for the next step?

Square calculator is the closest one after this: All four measures of a square from any one. Give the side, the area, the perimeter or the diagonal and it returns the rest — side s, area s², perimeter 4s and diagonal s√2 — instantly.

What else is worth having open alongside it?

Magic square generator and Equilateral triangle calculator — they come up in the same task often enough to be worth a second tab.

Further reading

All guides →
How-toHow to Calculate the Square Metres of a RoomFind a room's area by multiplying length by width. Here's the method for rectangular, L-shaped and round rooms, and why area drives your material orders.ExplainerThe Flat Pattern of a Cone Is a Sector, Not a CircleRoll a 50 mm cone 80 mm tall and its pattern is a 190.8° slice of a 94 mm circle. Flatten a nearly cylindrical lampshade and the pattern radius runs to 839 mm — the shallower the taper, the further away the apex.How-toHow to Find the Distance Between Two PointsUse the distance formula d = √((x₂−x₁)² + (y₂−y₁)²) to measure the straight-line distance between two points on a plane, with a worked example and the midpoint too.How-toHow to Calculate the Slope of a Line: Rise Over RunFind the slope of a line from two points with m = (y₂ − y₁) / (x₂ − x₁), and read what a positive, negative, zero, or undefined slope tells you.ExplainerThe Pythagorean Theorem ExplainedIn a right triangle, a² + b² = c². Here's what the formula means, a worked example, how to find any side, and where it's used in real life.How-toHow to Calculate VolumeVolume is the space inside a shape. Here's how to find it for boxes, cylinders and spheres, and why keeping your units consistent is the whole game.