Pi on Calculator: Formulas, Uses & Results
Get pi to as many decimals as you need, or compute circle and sphere measurements from a radius. And if you landed here looking for the pi button on your physical calculator, the guide below tells you exactly where it is on TI-84, Casio, iPhone and more.
Pi digits come from a stored 62-digit expansion; geometry uses full floating-point pi.
Worked example, checked against this exact tool
Pi digits: 10 decimals gives 3.1415926536. Circle area: radius 5 at 4 decimals: pi × 25 = 78.5398 sq units, with circumference 31.4159 shown alongside. Sphere volume: radius 5: (4/3) × pi × 125 = 523.5988 cu units. Enter the matching numbers to reproduce these figures.
Where is the pi button on a calculator?
If this is why you came, here is the answer for the common models. TI-84 Plus: press 2nd, then the ^ key (pi is its second function), and the pi symbol appears. Casio fx-991 (and most Casio scientifics): press SHIFT, then the ×10^x key, which carries pi as its second function. iPhone: open the Calculator app and rotate to landscape for the scientific layout, where the π key sits directly on the keypad. Android/Google calculator: the pi key is in the scientific panel (swipe up on the keypad in Google’s calculator). Windows Calculator: switch to Scientific mode and pi is on the keypad. Check your manual if your model differs; these cover the vast majority.
No pi button? Use these instead
Type 3.14159 (plenty for homework), 3.14159265358979 (the full double-precision value most calculators hold internally), or the fraction 355/113 = 3.1415929, accurate to six decimals. 22/7 = 3.142857 is the classic school approximation but is off in the third decimal, so prefer 355/113 when accuracy matters.
How many digits of pi do you actually need?
Fewer than you think. NASA uses 15 to 16 digits for the highest-precision trajectory calculations. 39 digits would compute the circumference of the observable universe to the precision of a hydrogen atom. For engineering, 3.14159 beats every measurement tool you own; for schoolwork, the pi button’s internal value (about 15 digits) is always the right choice over typing digits by hand.
What competing calculators miss
The “where is the pi button” guides (aeanet.org, calculatorov.com) answer the device question but give you no tool: you still have to do the geometry yourself. Circle calculators (Omni, calculator.net) do the geometry but never answer the device question that most searchers actually asked. This page does both: the button locations above, and a digits-plus-geometry tool that uses full-precision pi internally.
Frequently asked questions
Where is the pi button on a TI-84?
Press 2nd, then the ^ key. Pi is the second function of the caret key.
Where is pi on a Casio scientific calculator?
Press SHIFT, then the ×10^x key, which carries pi as its second function.
Where is pi on the iPhone calculator?
Rotate the Calculator app to landscape for the scientific layout; the π key is on the keypad.
What is pi to 10 decimal places?
3.1415926536. Use the tool above for any length from 1 to 50 decimals.
How do I type the pi symbol on a phone?
On iPhone, add the Greek keyboard in Settings › General › Keyboard and switch with the globe key. On Android, long-press is not standard; the Greek keyboard or a symbol app works.
What is 355/113?
A fraction equal to 3.1415929, accurate to six decimals: the best simple fraction approximation of pi.
How many digits of pi does NASA use?
15 to 16 digits for the highest-precision calculations, far fewer than most people assume.
What is the area of a circle with radius 5?
pi × 25 = 78.5398 square units. The tool computes this and shows the circumference alongside.