Welcome to our coterminal angle calculator - a tool that will solve many of your problems regarding coterminal angles:

  • Do you want to find a coterminal angle of a given angle, preferably in the [0, 360°) range? Great news: you can here.
  • Are you hunting for positive and negative coterminal angles? Also here.
  • Would you like to check if two angles are coterminal? Check! ✔️
  • Are you searching for a coterminal angles calculator for radians? Good for you, our tool works both for π radians and degrees.
  • Or maybe you're looking for a coterminal angles definition, with some examples? Then you won't be disappointed with this calculator.
  • Will the tool guarantee me a passing grade on my math quiz? ❌ Well, our tool is versatile, but that's on you :)

Use our calculator to solve your coterminal angles issues, or scroll down to read more.

What is a coterminal angle? Coterminal angles definition

Coterminal angles are those angles that share the terminal side of an angle occupying the standard position. The standard position means that one side of the angle is fixed along the positive x-axis, and the vertex is located at the origin.

In other words, two angles are coterminal when the angles themselves are different, but their sides and vertices are identical.

Also, you can remember the coterminal angles definition as angles that differ by a whole number of complete circles. Look at the picture below, and everything should be clear!


Image presenting three different coterminal angles to acute angle α: α - 360°, α+360° and α - 2*360°

So, as we said: all the coterminal angles start at the same side (initial side) and share the terminal side.

The thing which can sometimes be confusing is the difference between the reference angle and coterminal angles definitions. Remember that they are not the same thing - the reference angle is the angle between the terminal side of the angle and the x-axis, and it's always in the range of [0, 90] (or [0, π/2]).

How to find coterminal angles? Coterminal angles formula

To find the coterminal angles to your given angle, you need to add or subtract a multiple of 360° (or 2π if you're working in radians). So, to check whether the angles α and β are coterminal, check if they agree with a coterminal angles formula:

a) for angles measured in degrees

β = α ± 360 * k, where k is a positive integer

b) for angles measured in radians

β = α ± 2π * k, where k is a positive integer

A useful feature is that in trigonometry, any two coterminal angles have exactly the same trigonometric values. So if β and α are coterminal, then their sines, cosines and tangents are all equal.

How to find a coterminal angle between 0 and 360° (or 0 and 2π)?

To determine the coterminal angle between 0 and 360°, all you need to do is to use a modulo operation - in other words, divide your given angle by the 360° and check what the remainder is.

We'll show you how it works with two examples - covering both positive and negative angles. We want to find a coterminal angle with a measure of θ such that 0° ≤ θ < 360°, for a given angle equal to:


420°

  • 420 mod 360 = 60°

How to do it manually?

  • First, divide one number by the other, rounding down (towards the floor): 420/360 = 1
  • Then, multiply the divisor by the obtained number (called the quotient): 360 * 1 = 360
  • Subtract this number from your initial number: 420 - 360 = 60

Substituting these angles into the coterminal angles formula gives 420° = 60° + 360° * 1


-858°

  • -858 mod 360 = 222°

Repeating the steps from above:

  • -858 / 360 = -3
  • 360 * -3 = -1080
  • -858 + 1080 = 222

So the coterminal angles formula, β = α ± 360 * k, will look like this for our negative angle example:

-858° = 222° - 360° * 3

The same works for the [0,2π) range, all you need to change is the divisor - instead of 360, use 2π.

Now, check the results with our coterminal angle calculator - it displays the coterminal angle between 0 and 360° (or 0 and 2π), as well as some exemplary positive and negative coterminal angles.

Positive and negative coterminal angles

If you want to find a few positive and negative coterminal angles, you need to subtract or add a number of complete circles. But how many?


One method is to find the coterminal angle in the [0,360°) range (or [0,2π) range), as we did in the previous paragraph (if your angle is already in that range, you don't need to do this step). Then just add or subtract 360°, 720°, 1080°... (2π,4π,6π...), to obtain positive or negative coterminal angles to your given angle. For example, if α = 1400°, then the coterminal angle in the [0,360°) range is 320° - which is already one example of a positive coterminal angle.

  • other positive coterminal angles are 680°, 1040°...

  • other negative coterminal angles are -40°, -400°, -760°...


Also, you can simply add and subtract a number of revolutions, if all you need is any positive and negative coterminal angle. For our previously chosen angle, α = 1400°, let's add and subtract 10 revolutions (or 100, why not):

  • positive coterminal angle: β = α + 360 * 10 = 1400° + 3600° = 5000°

  • negative coterminal angle: β = α - 360 * 10 = 1400° - 3600° = -2200°

The number or revolutions must be large enough to change the sign when adding/subtracting. For example, one revolution for our exemplary α is not enough to have both a positive and negative coterminal angle - we'll get two positive ones, 1040° and 1760°.

What is a coterminal angle of...

If you're wondering what the coterminal angle of some angle is, don't hesitate to use our tool - it's here to help you!

But if, for some reason, you still prefer a list of exemplary coterminal angles (but we really don't understand why...), here you are:

  • Coterminal angle of 0°: 360°, 720°, -360°, -720°
  • Coterminal angle of 1°: 361°, 721°, -359°, -719°
  • Coterminal angle of 5°: 365°, 725°, -355°, -715°
  • Coterminal angle of 10°: 370°, 730°, -350°, -710°
  • Coterminal angle of 15°: 375°, 735°, -345°, -705°
  • Coterminal angle of 20°: 380°, 740°, -340°, -700°
  • Coterminal angle of 25°: 385°, 745°, -335°, -695°
  • Coterminal angle of 30° (π / 6): 390°, 750°, -330°, -690°
  • Coterminal angle of 45° (π / 4): 495°, 765°, -315°, -675°
  • Coterminal angle of 60° (π / 3): 420°, 780°, -300°, -660°
  • Coterminal angle of 75°: 435°, 795°,-285°, -645°
  • Coterminal angle of 90° (π / 2): 450°, 810°, -270°, -630°
  • Coterminal angle of 105°: 465°, 825°,-255°, -615°
  • Coterminal angle of 120° (2π / 3): 480°, 840°, -240°, -600°
  • Coterminal angle of 135° (3π / 4): 495°, 855°, -225°, -585°
  • Coterminal angle of 150° (5π / 6): 510°, 870°, -210°, -570°
  • Coterminal angle of 165°: 525°, 885°, -195°, -555°
  • Coterminal angle of 180° (π): 540°, 900°, -180°, -540°
  • Coterminal angle of 195°: 555°, 915°, -165°, -525°
  • Coterminal angle of 210° (7π / 6): 570°, 930°, -150°, -510°
  • Coterminal angle of 225° (5π / 4): 585°, 945°, -135°, -495°
  • Coterminal angle of 240° (4π / 3): 600°, 960°, 120°, -480°
  • Coterminal angle of 255°: 615°, 975°, -105°, -465°
  • Coterminal angle of 270° (3π / 2): 630°, 990°, -90°, -450°
  • Coterminal angle of 285°: 645°, 1005°, -75°, -435°
  • Coterminal angle of 300° (5π / 3): 660°, 1020°, -60°, -420°
  • Coterminal angle of 315° (7π / 4): 675°, 1035°, -45°, -405°
  • Coterminal angle of 330° (11π / 6): 690°, 1050°, -30°, -390°
  • Coterminal angle of 345°: 705°, 1065°, -15°, -375°
  • Coterminal angle of 360° (2π): 0°, 720°, -360°, -720°

If you didn't find your query on that list, type the angle into our coterminal angle calculator - you'll get the answer in the blink of an eye!

Hanna Pamuła, PhD candidate

Get the widget!

Coterminal Angle Calculator can be embedded on your website to enrich the content you wrote and make it easier for your visitors to understand your message.

It is free, awesome and will keep people coming back!

Coterminal Angles Calculator | Definition | Formulas