What the IN function does
The IN function converts a number from one unit of measurement to another. If your calculator has an IN button or menu option, it lets you change inches to centimeters, pounds to kilograms, gallons to liters, and dozens of other conversions without typing a formula yourself.
Different calculators name this feature differently — some call it IN, others call it CONV or CONVERT. The steps below work for most scientific and graphing calculators, though the exact button sequence varies by brand and model.
Key Takeaways
- The IN function converts measurements between units — type the number, press IN, choose your units, and the calculator shows the result.
- You need to know which unit you are starting with and which unit you want to convert to before you begin.
- Most calculators store IN conversions in a menu you access by pressing SHIFT, 2ND, or ALPHA before the IN button.
- If your calculator does not have an IN button, you can still convert by looking up the conversion factor and multiplying by hand.
- Common conversions include length (inches to centimeters), weight (pounds to kilograms), and volume (gallons to liters).
Finding the IN button or menu on your calculator
On most scientific calculators, the IN button sits on the keypad itself. On graphing calculators like the TI-84, IN is usually hidden in a menu. Look for a button labeled SHIFT, 2ND, or ALPHA — press it, then look at the small text printed above the number keys. The IN function is often printed above a key near the middle or right side of the keypad.
If you see IN printed above a key, press SHIFT (or 2ND or ALPHA, depending on your model) and then press that key. A menu will appear showing conversion categories like LENGTH, WEIGHT, VOLUME, or TEMPERATURE. If you cannot find IN anywhere on your calculator, check the manual that came with it — some older or basic models do not have this feature.
Converting a measurement step by step
Start by typing the number you want to convert. For example, if you want to change 5 inches to centimeters, type 5 into your calculator and press Enter or =.
Next, press the button that opens the IN menu — usually SHIFT or 2ND, then the IN key. A list of categories will appear on your screen. Use the arrow keys to highlight the category you need (LENGTH, WEIGHT, VOLUME, TEMPERATURE, or AREA). Press Enter to open that category.
A new menu will show the units within that category. For LENGTH, you might see IN (inches), CM (centimeters), FT (feet), M (meters), and others. Use the arrow keys to highlight the unit you are starting with — in this example, IN for inches. Press Enter.
The calculator will now ask you which unit you want to convert to. Highlight CM (centimeters) and press Enter. The calculator will show the result: 5 inches equals 12.7 centimeters.
Common conversions and which menu to use
Most calculators organize conversions into five main categories. LENGTH includes inches, feet, centimeters, meters, miles, and kilometers. WEIGHT includes ounces, pounds, grams, and kilograms. VOLUME includes cups, pints, gallons, milliliters, and liters. TEMPERATURE converts Fahrenheit to Celsius and back. AREA converts square inches to square centimeters and similar units.
If you are not sure which category your conversion belongs to, think about what the number measures. If it measures how long something is, use LENGTH. If it measures how heavy something is, use WEIGHT. If it measures how much space something takes up, use VOLUME. Temperature is the only one that does not fit this pattern — it measures how hot or cold something is.
What to do if your calculator does not have IN
If your calculator has no IN button or menu, you can still convert by hand using a conversion factor. A conversion factor is a number that tells you how many of one unit equal one of another unit. For example, 1 inch equals 2.54 centimeters, so the conversion factor is 2.54.
To convert, multiply your starting number by the conversion factor. If you want to convert 5 inches to centimeters, multiply 5 × 2.54 = 12.7. You can find conversion factors online or in a reference table. This method takes a few extra steps, but it works on any calculator that can multiply.
Fixing mistakes and common errors
If you see a result that looks wrong, check that you chose the correct starting unit. A common mistake is selecting the unit you want to convert to instead of the unit you are starting with. If you typed 5 and meant to convert from inches, make sure you highlighted IN (not CM) when the calculator asked which unit you started with.
Another mistake is using the wrong category. Temperature conversions work differently than other conversions — Fahrenheit to Celsius is not a simple multiplication, so if your temperature result looks odd, double-check that you used the TEMPERATURE menu and not LENGTH or WEIGHT by accident.
If the result is way too large or too small, you may have typed the wrong starting number. Clear the calculator by pressing the C or CLEAR button and start over. Type your number slowly and check it on the screen before pressing Enter.
Converting multiple numbers in a row
If you need to convert several numbers using the same units, you do not have to open the IN menu each time. After your first conversion, type a new number and press Enter. Then press SHIFT (or 2ND) and IN again. The calculator will often remember the units you just used and show you the conversion menu faster the second time.
Some calculators let you stay in the IN menu and just type new numbers without closing it. Check your calculator's manual to see if this is possible on your model. This feature saves time if you are converting a long list of measurements.
Frequently Asked Questions
Can I convert from centimeters to inches instead of inches to centimeters?
Yes. The IN function works both ways. Type your number, open the IN menu, choose LENGTH, select CM as your starting unit, then select IN as your target unit. The calculator will convert from centimeters to inches just as easily as the other direction.
Why does my temperature conversion look wrong?
Temperature conversions use a different formula than other units because they have different starting points. Celsius and Fahrenheit do not start at zero the same way inches and centimeters do. Make sure you are using the TEMPERATURE menu, not LENGTH. If you used the wrong menu, clear and try again.
What if my calculator shows a decimal with many digits?
That is normal. Conversions often produce long decimals. You can round the answer to fewer decimal places if you need a simpler number. For example, 5 inches equals 12.7 centimeters exactly, but your calculator might show 12.700000001 due to how it stores numbers internally.
Can I convert between units that are not in the IN menu?
If your calculator does not have a specific conversion built in, you can look up the conversion factor and multiply by hand. For example, if you want to convert tablespoons to milliliters and your calculator does not have that option, find that 1 tablespoon equals 14.787 milliliters, then multiply your number by 14.787.
Do I need to clear the calculator between conversions?
No. You can type a new number and open the IN menu again without pressing CLEAR. However, if you want to make sure you are starting fresh, pressing C or CLEAR before typing your next number is a safe habit.