Choose the direction of the conversion and enter the numbers. For "rectangular → polar", enter the x- and y-coordinates. For "polar → rectangular", enter the radius r and the angle θ (and choose its unit).
Table of Contents
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What you can do on this page
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What is this calculation used for?
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How to Use
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Formulas and figures
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Symbols and terms
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Good to know before you start
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How to calculate it in Excel
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How to calculate it in Google Sheets
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How to calculate it in Python
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How to write it in LaTeX and other math languages (copy and paste)
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How to have ChatGPT do the calculation
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DataChef Features
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Related Features
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NumberChef Calculators List
What you can do on this page
- Convert rectangular coordinates \(P(x,\ y)\) to polar coordinates \(P(r,\ \theta)\) on the spot. The radius is given as an exact value with a simplified root, such as \(\sqrt{8} = 2\sqrt{2}\), and for special angles the angle is given exactly as a fraction of π
- The angle \(\theta\) is given mainly in the range \(0 \le \theta < 2\pi\), with the value for \(-\pi < \theta \le \pi\) shown too, so you can check your answer whichever range your textbook uses
- You can also convert the other way (polar → rectangular). Enter the radius \(r\) and the angle \(\theta\) (in degrees, as a fraction of π, or in radians as a decimal), and you get \(x = r\cos\theta\) and \(y = r\sin\theta\) as exact values such as \(\left(-2,\ 2\sqrt{3}\right)\)
- The steps show, one at a time, how the angle is decided from \(\tan\theta = \dfrac{y}{x}\) and the quadrant the point is in (the quadrant adjustment)
- You can check the result on a figure of the coordinate plane. Light concentric circles (a scale for the radius) and rays (a scale for the angle) show at a glance where the radius \(r\) and the angle \(\theta\) are
What is this calculation used for?
Airport radar and ship radar measure "the distance from here" by the time a radio pulse takes to bounce back, and "the bearing" by the direction the antenna is pointing. So what they measure is polar coordinates \(\left(r,\ \theta\right)\) from the start.
But the controller's screen and nautical charts are built on horizontal and vertical coordinates, so inside the equipment the measured distance and bearing are converted to rectangular coordinates with \(x = r\cos\theta\) and \(y = r\sin\theta\). This page's conversion is what connects a device that measures by distance and direction with a screen that draws across and up.
The laser distance sensors (LiDAR) on self-driving cars and robot vacuums spin around and take a huge number of measurements of the form "something reflected the beam this far away in this direction". Each measurement is a pair of direction (angle) and distance, which is polar coordinates.
To build a map from the collected points, every point is converted to rectangular coordinates and then combined. Mapping the surroundings and then planning a route is the basic flow of self-driving, and this coordinate conversion is where it starts.
Weather radar also spins its antenna while sending out radio waves, and receives the reflections from rain and snow as "bearing and distance". The rain images in TV weather forecasts are this polar data converted to the horizontal and vertical coordinates of a map.
Giving the position of a hurricane as "150 miles south-southeast of Miami" is also the polar way of thinking, and the conversion to rectangular coordinates happens when the point is plotted on a map.
For things that turn around a center, such as the cars on a Ferris wheel, the teeth of a gear or the blades of a fan, design gets simpler if you think "the distance from the center is fixed and only the direction changes". In polar coordinates you just fix the distance \(r\) and change the angle \(\theta\), which makes placing the parts very easy.
But drawings and CNC machine tools take horizontal and vertical coordinates, so at the end every position is converted to rectangular coordinates before it is handed over.
Placing enemies evenly around the hero, firing bullets in all directions, orbiting a camera around a target: these are most natural to think of in terms of "distance from the center" and "angle", and splitting the angle evenly decides the layout.
The screen is drawn in horizontal and vertical coordinates, so every frame the positions are converted with \(x = r\cos\theta\) and \(y = r\sin\theta\). This conversion is why circular motion is easy to program.
Formulas and figures
Symbols and terms
Symbols
| \(P\) | pee | A letter often used for a point in the plane, from the first letter of "point". The coordinates of the point are written in the parentheses after it, as in \(P\left(1,\ 2\right)\). |
| \(O\) | oh | The letter for the origin (the pole), from the first letter of "origin". In polar coordinates, distances are measured from this point. |
| \(x,\ y\) | x, y | The horizontal (\(x\)-axis direction) and vertical (\(y\)-axis direction) positions in rectangular coordinates. Both can be negative. |
| \(r\) | are | The letter for the radius (the distance from the pole to the point), from the first letter of "radius". In polar coordinates it is a real number 0 or greater. |
| \(\theta\) | theta | The Greek letter used for the angle. In math it is the usual letter for an angle. |
| \(\left(r,\ \theta\right)\) | r, theta | How polar coordinates are written: first the distance (radius), then the direction (angle). It looks just like rectangular \(\left(x,\ y\right)\), so always say which kind of coordinates you are using. |
| \(\cos\theta,\ \sin\theta\) | cosine theta, sine theta | Trigonometric ratios (trigonometric functions). On the circle of radius 1 (the unit circle), the point in the direction of the angle \(\theta\) has horizontal position \(\cos\theta\) and vertical position \(\sin\theta\). They are the key to converting polar to rectangular. |
| \(\tan\theta\) | tangent theta | One of the trigonometric ratios, defined as \(\tan\theta = \dfrac{\sin\theta}{\cos\theta}\). On the coordinate plane, \(\tan\theta = \dfrac{y}{x}\) (rise over run, the slope of the line through the origin and the point), which is the clue for finding the angle. |
| \(\arctan\) | arctangent | The inverse of the tangent (also written \(\tan^{-1}\)). It returns the angle \(\theta\) with \(\tan\theta = k\). The angles it returns are limited to between \(-\dfrac{\pi}{2}\) and \(\dfrac{\pi}{2}\), so a quadrant adjustment is needed for angles in Quadrants II and III. |
| \(\pi\) | pi | The ratio of a circle's circumference to its diameter (about 3.14159). In radian measure, a half turn, \(180^{\circ}\), is exactly \(\pi\). The Greek letter \(\pi\) is said to come from the first letter of the Greek word for "perimeter". |
| \(n\) | en | A letter often used for an integer, from the first letter of "number". On this page it is how many full turns the angle is shifted, including negative integers (turning the other way) and 0 (no turn). |
Terms
| rectangular coordinates | A way to give the position of a point as a pair \(\left(x,\ y\right)\): how far across and how far up. These are the everyday coordinates used since middle school, also called Cartesian coordinates. |
| polar coordinates | A way to give the position of a point as a pair \(\left(r,\ \theta\right)\): the distance \(r\) from a reference point and the angle \(\theta\) from a reference direction. They are taught in Precalculus. |
| pole | The reference point from which distances are measured in polar coordinates. On the coordinate plane it is placed at the origin \(O\). |
| polar axis | The reference ray from which angles are measured in polar coordinates. It starts at the pole, and on the coordinate plane it lies along the positive \(x\)-axis. |
| radius | The distance \(r\) from the pole to the point \(P\) (also called the radial coordinate). Strictly, the segment (or ray) joining the pole and \(P\) is also meant, with length \(r\). It is 0 or greater. |
| angle θ | The angle \(\theta\) of the direction from the pole to the point \(P\), measured counterclockwise from the polar axis (also called the polar angle or argument). Adding a full turn (\(2\pi\)) gives the same direction, so answers are usually given in a range such as \(0 \le \theta < 2\pi\) or \(-\pi < \theta \le \pi\). |
| quadrant | One of the four regions the two axes divide the coordinate plane into. The upper right is Quadrant I, and counting counterclockwise from there come Quadrants II, III and IV. Knowing which quadrant a point is in is the clue for fixing the angle. |
| quadrant adjustment | Within one full turn, two angles satisfy \(\tan\theta = \dfrac{y}{x}\), so you choose the one that matches the quadrant of the point (for example, by adding \(\pi\) to the acute angle from \(\arctan\)). This fix is the quadrant adjustment. |
| unit circle | The circle of radius 1 centered at the origin. The point on it in the direction of the angle \(\theta\) is \(\left(\cos\theta,\ \sin\theta\right)\), which is the basis of the polar conversion formulas. |
| radian measure | Measuring an angle by the length of the arc on a circle of radius 1. \(180^{\circ} = \pi\) radians. From trigonometric functions in Algebra 2 and Precalculus on, radians are the standard unit rather than degrees. |
| special angles | \(30^{\circ}\), \(45^{\circ}\), \(60^{\circ}\) and the angles related to them (these plus multiples of \(90^{\circ}\)). Their trigonometric ratios can be written exactly, such as \(\dfrac{1}{2}\), \(\dfrac{\sqrt{2}}{2}\) and \(\dfrac{\sqrt{3}}{2}\), and most textbook and test problems use them. |
| polar equation | An equation of a curve written as a relationship between \(r\) and \(\theta\). For example, \(r = 2\) is the circle of radius 2 centered at the origin, and \(\theta = \dfrac{\pi}{4}\) is the ray from the origin with slope 1. Figures determined by the distance from a center, such as circles and spirals, have much simpler equations than in rectangular coordinates. |
Good to know before you start
Here is what helps you use the calculation on this page with real understanding, not just by pressing the button.
If you get stuck, going back to review these topics is the fastest way forward.
| The coordinate plane (Grades 5–6) |
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| Square roots and radicals (Grade 8 and Algebra 1) |
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| The Pythagorean theorem (Grade 8) |
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| Trigonometric ratios and the unit circle (Geometry, Algebra 2 and Precalculus) |
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| Radian measure (Algebra 2 and Precalculus) |
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| Polar coordinates (Precalculus) |
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How to calculate it in Excel
| x-coordinate | 3 |
| y-coordinate | 4 |
| Radius r | =SQRT(B1^2+B2^2) |
| Angle θ (radians, 0 ≤ θ < 2π) | =MOD(ATAN2(B1,B2),2*PI()) |
| Angle θ (degrees) | =DEGREES(MOD(ATAN2(B1,B2),2*PI())) |
| Radius r | 2 |
| Angle θ (degrees) | 60 |
| x-coordinate = r cosθ | =B1*COS(RADIANS(B2)) |
| y-coordinate = r sinθ | =B1*SIN(RADIANS(B2)) |
| Angle θ (degrees) | 60 |
| Number of turns n (integer, may be negative) | 1 |
| Shifted angle (degrees) | =B1+360*B2 |
In the first table, ATAN2(x-coordinate, y-coordinate) returns the angle with the quadrant adjustment already done (more than −π and up to π). Taking MOD with 2π turns it into an angle from 0 up to (but not including) 2π. For the example point (3, 4), r = 5 and θ ≈ 0.9273 (about 53.13 degrees).
In the second table, RADIANS converts degrees to radians. For the example r = 2 and θ = 60 degrees, x = 1 and y ≈ 1.7320508 (= √3). Excel gives decimal answers, so use the calculator on this page when you want exact values such as √3 or fractions of π.
The third table makes other polar coordinates for the same point. Adding one full turn, 360 degrees, to the example 60 degrees gives 420 degrees. With n = −1 you get −300 degrees, and all of these are the same point.
How to calculate it in Google Sheets
| x-coordinate | 3 |
| y-coordinate | 4 |
| Radius r | =SQRT(B1^2+B2^2) |
| Angle θ (radians, 0 ≤ θ < 2π) | =MOD(ATAN2(B1,B2),2*PI()) |
| Angle θ (degrees) | =DEGREES(MOD(ATAN2(B1,B2),2*PI())) |
| Radius r | 2 |
| Angle θ (degrees) | 60 |
| x-coordinate = r cosθ | =B1*COS(RADIANS(B2)) |
| y-coordinate = r sinθ | =B1*SIN(RADIANS(B2)) |
| Angle θ (degrees) | 60 |
| Number of turns n (integer, may be negative) | 1 |
| Shifted angle (degrees) | =B1+360*B2 |
How to calculate it in Python
import math
# Rectangular → polar
x_coordinate = 3
y_coordinate = 4
radius = math.sqrt(x_coordinate ** 2 + y_coordinate ** 2)
argument = math.atan2(y_coordinate, x_coordinate) # includes the quadrant adjustment (−π < θ ≤ π)
if argument < 0:
argument += 2 * math.pi # move into the range 0 ≤ θ < 2π
print(f"Radius r = {radius}")
print(f"Angle θ = {argument} rad ({math.degrees(argument)} degrees)")
# Polar → rectangular
r = 2
theta_degree = 60
theta = math.radians(theta_degree)
print(f"x-coordinate = {r * math.cos(theta)}")
print(f"y-coordinate = {r * math.sin(theta)}")
How to write it in LaTeX and other math languages (copy and paste)
x = r cosθ, y = r sinθ
x = r\cos\theta,\quad y = r\sin\theta
<math xmlns="http://www.w3.org/1998/Math/MathML" display="block">
<mtable columnalign="left">
<mtr><mtd>
<mi>x</mi><mo>=</mo><mi>r</mi><mi>cos</mi><mi>θ</mi>
</mtd></mtr>
<mtr><mtd>
<mi>y</mi><mo>=</mo><mi>r</mi><mi>sin</mi><mi>θ</mi>
</mtd></mtr>
</mtable>
</math>
x = r cos theta, y = r sin theta
{x, y} = {r Cos[theta], r Sin[theta]}
x := r*cos(theta); y := r*sin(theta);
[x, y] = pol2cart(theta, r);
x = r cos θ, y = r sin θ
r = √(x² + y²)
r = \sqrt{x^{2} + y^{2}}
<math xmlns="http://www.w3.org/1998/Math/MathML" display="block">
<mrow>
<mi>r</mi>
<mo>=</mo>
<msqrt>
<mrow>
<msup><mi>x</mi><mn>2</mn></msup>
<mo>+</mo>
<msup><mi>y</mi><mn>2</mn></msup>
</mrow>
</msqrt>
</mrow>
</math>
r = sqrt(x^2 + y^2)
r = Sqrt[x^2 + y^2]
r := sqrt(x^2 + y^2);
r = hypot(x, y);
r = √(x^2 + y^2)
tanθ = y/x
\tan\theta = \dfrac{y}{x}
<math xmlns="http://www.w3.org/1998/Math/MathML" display="block">
<mrow>
<mi>tan</mi><mi>θ</mi>
<mo>=</mo>
<mfrac><mi>y</mi><mi>x</mi></mfrac>
</mrow>
</math>
tan theta = y/x
theta = ArcTan[x, y]
theta := arctan(y, x);
theta = atan2(y, x);
tan θ = y/x
(r, θ) = (r, θ + 2nπ)
\left(r,\ \theta\right) = \left(r,\ \theta + 2n\pi\right)
<math xmlns="http://www.w3.org/1998/Math/MathML" display="block">
<mrow>
<mo>(</mo><mi>r</mi><mo>,</mo><mi>θ</mi><mo>)</mo>
<mo>=</mo>
<mo>(</mo><mi>r</mi><mo>,</mo>
<mi>θ</mi><mo>+</mo><mn>2</mn><mi>n</mi><mi>π</mi>
<mo>)</mo>
</mrow>
</math>
(r, theta) = (r, theta + 2 n pi)
theta + 2 n Pi
theta + 2*n*Pi;
theta2 = theta + 2*n*pi;
(r, θ) = (r, θ + 2nπ)
How to have ChatGPT do the calculation
You are a math assistant for polar coordinates in the plane. Do the following calculation by actually running Python code, and base your answer only on the numbers from the execution result (do not answer by mental math or guessing). 1. Convert the point (3, 4) in rectangular coordinates to polar coordinates (r, θ). Show the radius r and the angle θ (in the range 0 ≤ θ < 2π, in both radians and degrees). 2. Convert the point (2, 60°) in polar coordinates to rectangular coordinates (x, y). Show x and y as decimals and, if possible, as exact values with √. In Python, use math.atan2 and math.sqrt, and show the formulas you used and the numbers from the execution result.
How to Use
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1Enter your numbersType the numbers you want to calculate with into the input fields
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2CalculatePress the "Calculate" button
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3Check the resultThe result appears on the spot. The same page also explains the idea behind the calculation and the formula
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