Math calculators

Pi Calculator

Updated Aug 14, 2026 By Jehan Wadia
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RAD Expression
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Result
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Angle mode
Scientific functions
Keyboard supported: 0–9 digits, + - * / ^ operators, . decimal, P inserts π, E inserts e, ( ) brackets, Enter evaluate, Backspace delete, Esc all clear.
Result Details
Calculation History (0 of 20)
    Step-by-Step Solution
    Your Result Compared With Common π Values

    Introduction

    This Pi Calculator helps you do math with π (pi) fast. Pi is about 3.14159, and it shows up in circles, angles, waves, and lots of geometry problems. Instead of typing 3.14 by hand, just tap the π key and get a full-precision answer.

    You can add, subtract, multiply, divide, and use powers. Open the Advanced panel for square roots, nth roots, sine, cosine, tangent, logs, and e. Switch between radians (RAD) and degrees (DEG) with one tap, and pick how many decimal places you want to see. If you only need basic arithmetic, our Simple Calculator is a lighter option, and for very long digit strings try the Arbitrary Precision Calculator.

    Every answer comes with a step-by-step solution, so you can see how the math works, not just the final number. The Result Details box also shows your answer as a multiple of π, in degrees, in radians, and in scientific notation. A chart compares your result to common pi values like π, 2π, π/2, and π². Your last 20 calculations are saved in the history list, and you can click any of them to use it again.

    How to use our Pi Calculator

    Type a math problem that uses pi, then read the answer. The calculator shows your result, extra details, a step-by-step solution, and a chart that compares your answer to common pi values.

    Number and operator keys: Tap the digits 0–9, the decimal point, and the signs +, −, ×, ÷, or ^ to build your problem. For power-only work, the Exponent Calculator handles bases and exponents on their own.

    π key: Tap the big purple π button to add pi (3.14159…) to your expression.

    Angle mode (RAD or DEG): Pick RAD if your angles are in radians, or DEG if they are in degrees. This changes answers for sin, cos, and tan. See the Trig Calculator or the Angle Calculator for angle-focused problems.

    Result precision: Choose how many decimal places you want to see, or leave it on Auto for 10 significant digits. The Sig Fig Calculator and Rounding Calculator explain how rounding rules work.

    Advanced button: Tap Advanced to open extra science keys like square root, nth root, powers, logs, e, and inverse trig functions such as arcsin and tan inverse.

    ( ) and (−) keys: Use the bracket key to group parts of your problem, and the (−) key to make the last value negative.

    AC and DEL keys: Press DEL to erase one entry, or AC to clear everything and start over.

    = or Calculate button: Press either one to solve your problem and save it to your history.

    Copy button: Tap Copy to put the answer on your clipboard so you can paste it somewhere else.

    Calculation History: Tap any past problem to load it back into the calculator, or press Clear History to empty the list.

    Reset button: Press Reset to return to the sample problem and the default settings.

    Keyboard: You can also type numbers and operators, press P for pi, E for e, Enter to solve, Backspace to delete, and Esc to clear.

    What Is Pi (π)?

    Pi is a number that shows up in every circle. If you measure the distance around a circle (the circumference) and divide it by the distance across it (the diameter), you always get pi. It does not matter if the circle is a coin or a planet — the answer is the same. Our Diameter to Circumference Calculator does that conversion in one step.

    Pi starts like this: 3.14159265358979... The digits never end and never repeat in a pattern. That makes pi an irrational number. Because it never ends, we round it. Most school work uses 3.14 or the fraction 22/7 — you can compare those with the Fraction to Decimal Calculator. Engineers and scientists often use more digits, like 3.14159265.

    Formulas That Use Pi

    In these formulas, r is the radius (half the width of the circle) and h is the height. For curved sections of a circle, the Arc Length Calculator uses the same constant, and the Perimeter Calculator covers straight-sided shapes.

    Pi and Angles

    Pi is also used to measure angles in radians. A full turn around a circle is 2π radians, which equals 360°. So half a turn is π radians (180°), and a quarter turn is π/2 radians (90°). To change radians into degrees, multiply by 180/π. To change degrees into radians, multiply by π/180. This matters when you use sine, cosine, and tangent, since the answer changes based on whether you work in radians (RAD) or degrees (DEG). The Cos Calculator, Triangle Angle Calculator, and Law of Sines Calculator all rely on the same angle rules.

    Handy Pi Values

    • π ≈ 3.141592654
    • 2π ≈ 6.283185307
    • π/2 ≈ 1.570796327
    • π/4 ≈ 0.785398163
    • π² ≈ 9.869604401
    • 1/π ≈ 0.318309886

    Where Pi Is Used

    Pi is not just for math class. It helps people find the size of pipes and wheels, build round tanks, plan gears and engines, track waves and sound, and figure out orbits in space. Practical examples include the Pipe Volume Calculator, the Tank Volume Calculator, the Gear Ratio Calculator, the Wavelength Calculator, and the Frequency Calculator. Even game builders use it — try the Minecraft Circle Calculator. Any time something spins, curves, or repeats, pi is usually part of the math.

    A Little History

    People have studied pi for thousands of years. Ancient Babylonians and Egyptians used rough values close to 3.125 and 3.16. Around 250 BC, the Greek thinker Archimedes drew shapes inside and outside a circle to prove pi sits between 3⅞₁ and 3⅝. The Greek letter π became the common symbol in the 1700s, thanks in part to the mathematician Leonhard Euler. Today, computers have found trillions of digits of pi, but for almost all real work, a few digits are plenty. If you enjoy famous constants, the Golden Ratio Calculator and the Fibonacci Calculator explore two more.

    Formulas used

    Degree to radian conversion for trigonometric input
    \theta_{\text{rad}} = \theta_{\deg} \times \frac{\pi}{180}
    Radian to degree conversion for inverse trigonometric output
    \theta_{\deg} = \theta_{\text{rad}} \times \frac{180}{\pi}
    Base-10 logarithm from natural logarithm
    \log_{10}(x) = \frac{\ln(x)}{\ln(10)}
    Nth root as a fractional power
    \sqrt[n]{x} = x^{\frac{1}{n}}
    Percent conversion
    x\% = \frac{x}{100}
    Reciprocal
    f(x) = \frac{1}{x}
    Result expressed as a multiple of pi
    k = \frac{v}{\pi} \quad \Rightarrow \quad v = k \times \pi
    Odd nth root of a negative number
    \sqrt[n]{x} = -\left(-x\right)^{\frac{1}{n}}, \quad x < 0,\ n \text{ odd}

    Frequently asked questions

    How many digits of pi does this calculator use?

    It uses pi to about 15 digits: 3.14159265358979. That is far more exact than 3.14 or 22/7, so your answers stay accurate. You only see fewer digits because of the precision setting you pick.

    Does the calculator follow order of operations?

    Yes. It follows PEMDAS. Brackets go first, then powers, then multiply and divide, then add and subtract. So 2 + 3 × π multiplies first, giving about 11.42. Use brackets if you want the adding done first.

    How do I type 2π without a times sign?

    Just tap 2 and then the π key. The calculator reads a number next to π as multiplication, so 2π gives 6.283185307. The same trick works for 4π or 2πr style problems.

    Why does my answer show three dots instead of a number?

    The dots mean your expression is not finished yet. This happens when it ends with an operator, an open bracket, or a function with no number in it. Add the missing part and the answer appears.

    Do I have to close every bracket?

    No. If you leave brackets open at the end, the calculator closes them for you when it solves. Still, closing them yourself is safer when you have brackets inside brackets.

    What does Result ÷ π mean in the Result Details box?

    It shows your answer written as a multiple of pi. For example, if your result is 6.2832, then Result ÷ π is 2, so the answer is 2π. This is handy for trig and radian homework where teachers want answers like π/2 or 3π/4.

    Why does sin(π) show 0 and not a tiny number?

    Computers store pi with a tiny bit of rounding, so sin(π) really comes out as something like 0.0000000000000001. The calculator cleans up values that small and shows a clean 0, which is the correct math answer.

    Why does tan(π/2) give an error?

    Tangent has no value at π/2 (90°) because the cosine there is zero, and you cannot divide by zero. The calculator shows Error: Undefined. The same thing happens at 3π/2, 270°, and every half turn after that.

    What does Error: Undefined (domain) mean?

    It means the number you typed is not allowed for that function. Common causes:

    • Square root of a negative number
    • log or ln of zero or a negative number
    • asin or acos of a number outside −1 to 1

    Check your input and try again.

    Why do I get Error: Invalid expression?

    Something in the expression does not make sense to the calculator, like two operators in a row or a missing number inside a function. Press DEL to fix the last part, or AC to start fresh.

    How do I use the nth root key?

    Tap the ⁿ√ key, type the root number, tap the comma key, then type the value. For a cube root of 8 you enter ⁿ√(3, 8) and get 2.

    What is the difference between the (−) key and the minus key?

    The − key subtracts one number from another. The (−) key flips the sign of the last value, turning 5 into −5. Use (−) when you need a negative number, not a subtraction.

    How do I find the area of a circle here?

    Type π × r ^ 2, using your radius for r. For a radius of 5, enter π × 5 ^ 2 to get about 78.54. For a full breakdown, try the Circle Area Calculator.

    What does the % key do?

    It divides the value before it by 100. So 25% becomes 0.25. You can then multiply it by anything, like 25% × π, which gives about 0.7854.

    Why is my answer shown as 1.5e+16?

    That is scientific notation, used when a number is very big or very small. 1.5e+16 means 1.5 × 10¹⁶. Learn more with the Scientific Notation Calculator.

    What does Auto precision mean?

    Auto shows 10 significant digits, so it counts all digits, not just the ones after the decimal point. Pick a set number like 5 or 15 decimal places if your teacher or job needs an exact count.

    Does the Copy button copy all the digits?

    Copy grabs exactly what you see in the result line. If you want more digits, change Result precision to 15 decimal places first, then tap Copy.

    Is my history saved after I close the page?

    No. The history list only lasts while the page is open. Copy any answer you want to keep before you leave or refresh.

    Why is e on the keypad if this is a pi calculator?

    e is another famous math number, about 2.71828. It shows up in growth, decay, and logs. Having it next to π lets you solve science problems that use both.

    Can I use this calculator on my phone?

    Yes. It works in any browser on a phone, tablet, or computer. It is free, needs no sign-up, and no download.

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