How do I calculate the distance between two points?

Subtract the coordinates of one point from the other along each axis, square each difference, add them together and take the square root. For 0,0 to 3,4 that is the square root of 9 plus 16, which is exactly 5.

How do I convert miles to kilometres?

One international mile is exactly 1,609.344 metres and one kilometre is exactly 1,000 metres, so one mile is exactly 1.609344 kilometres. Using the familiar 1.6 figure introduces a 0.58 percent error.

How many feet are in a mile?

Exactly 5,280 feet, since a mile is exactly 1,609.344 metres and a foot is exactly 0.3048 metres. A yard is exactly 3 feet and an inch is exactly one twelfth of a foot.

What is a nautical mile?

Exactly 1,852 metres, tied to one minute of arc of latitude rather than to any land survey. It is deliberately different from the statute mile, and it is why navigation speeds are quoted in knots, one nautical mile per hour.

How do I calculate a hypotenuse?

Square both legs, add them and take the square root. Legs of 5 and 12 give the square root of 25 plus 144, which is the square root of 169, which is exactly 13.

Does the calculator work in 3D?

Yes. Switch the dimensions selector to 3D and the z coordinate is included as a third squared term. The calculator also reports the change along each axis separately so you can see which contributes most.

What is the midpoint between two points?

Average each coordinate independently. The midpoint of 0,0 and 10,20 is 5,10, found by adding the two x values, dividing by two, and doing the same for y.

Is straight line distance the same as travel distance?

No. The straight line is a lower bound. Roads, rivers, buildings and terrain always add distance, sometimes considerably. Use the straight line to compare relative positions rather than to estimate a journey.

Why do my conversions drift slightly?

Usually because a rounded conversion factor was used, such as 1 mile as 1.6 kilometres. Every unit here is an exact defined constant, so converting there and back returns the original value exactly.

Can this calculate distance on a sphere?

Not directly. This calculates straight line distance in flat Cartesian space, which is correct for buildings, plans, screens and small areas. For long distances on the Earth's curved surface a haversine or great circle calculation is needed instead.

How to Use the Distance Calculator

Three modes in one calculator: distance between two points in 2D or 3D, exact conversion between nine distance units, and the hypotenuse of a right angled triangle.

Step-by-Step Instructions

1 Choose what you want from the first dropdown: distance between points, convert between units, or the hypotenuse from two sides.
2 For points, choose 2D or 3D and enter the coordinates for point A and point B.
3 For units, enter the value and pick the source and target units. Every conversion is exact and all nine appear at once.
4 For Pythagoras, enter the two leg lengths and read the hypotenuse along with the area and perimeter.
5 Use the How this is worked out panel to copy the calculation into your own working.

Understanding the Inputs

points

Two points as coordinates. In 2D these are x and y for each point. In 3D an extra z coordinate is added for each point.

How to find it: Coordinates from a map, a graph, a game engine, a survey or a spreadsheet. Order within the pair does not matter, since the distance is the same either way round.

Why it matters: Distance is invariant under swapping the two points, which this calculator relies on, and it holds regardless of the units the axes use as long as both axes share them.

units

A single distance value plus a source unit and a target unit, chosen from kilometres, metres, centimetres, millimetres, miles, yards, feet, inches and nautical miles.

How to find it: Anything mixing metric and imperial, such as a running distance in miles reported against a training plan in kilometres, or a nautical chart distance against a road distance.

Why it matters: Each unit is an exactly defined constant, so conversions are exact rather than rounded, and they round trip back to the original value without drift.

sides

The two leg lengths of a right angled triangle, from which the hypotenuse is found using the Pythagorean theorem.

How to find it: Any right triangle, or any situation where you know the two perpendicular offsets and need the diagonal, such as checking whether a ladder clears a wall.

Why it matters: The hypotenuse is the diagonal of the right triangle formed by the two perpendicular sides, and it is the shortest distance between two points given those two offsets.

Tips & Best Practices

✓ Use exact unit definitions rather than the rounded figures you remember.
✓ Swap the two points freely if it makes the subtraction easier to follow.
✓ Round only the final answer, never the intermediate squared terms.
✓ Remember the straight line is a lower bound for any real journey.

Try the Distance Calculator

by CalculatorPro Tools · Updated 10-12-2026