電卓 水色 - Calculator Water Blue
電卓 水色, or Calculator Water Blue, is a deliberately simple calculator. A soft sky-blue display, four operator keys and a large number pad are all there is, so nothing gets in the way of adding up a receipt, splitting a bill or checking a quick figure.
It works like a familiar pocket calculator: you type a number, press an operator, type the next number and press equals, and each step is calculated in the order you enter it. Results are rounded to twelve significant digits, so the tiny floating-point errors that make some apps show 0.30000000000000004 for 0.1 + 0.2 never appear.
There is no account, no history to manage and nothing stored. Open the page on your phone, tablet or computer and start calculating.
The app runs entirely in your browser. What you enter is saved only on this device.
How to use 電卓 水色
- Enter a number. Tap the digit keys. Use the dot key for decimals. Up to 12 digits can be entered.
- Choose an operation. Tap +, −, × or ÷ in the operator row. The selected operator stays highlighted while you type the next number.
- Get the result. Enter the second number and tap =. You can also chain operations: 2 + 3 × 4 is calculated as (2 + 3) × 4 = 20, step by step.
- Fix a typo. Tap the backspace key to delete the last digit you entered.
- Start again. Tap ac to clear everything. After an Error, such as dividing by zero, tap a digit or ac to start a fresh calculation.
Features
- Addition, subtraction, multiplication and division
- Large, easy-to-tap keys
- Highlighted operator while entering the next number
- Backspace for the last digit
- AC to clear everything
- Results rounded to 12 significant digits
- Scientific notation for very large or very small results
- Error message for division by zero
How simple calculators work out your sums
Immediate execution versus formula order
There are two common ways calculators handle a chain of operations. Basic and pocket calculators use immediate execution: each operation is carried out as soon as you press the next operator, so 2 + 3 × 4 becomes 5 × 4 = 20. Scientific calculators and spreadsheets follow the mathematical order of operations, multiplying before adding, which gives 14. Calculator Water Blue works the first way. When you need multiplication first, calculate that part on its own and then add.
Why 0.1 + 0.2 is not always 0.3
Computers store decimal numbers in binary, and many simple decimals such as 0.1 cannot be represented exactly. The tiny difference shows up when results are printed with every digit, giving answers like 0.30000000000000004. Rounding the result to a sensible number of significant digits, as this calculator does with twelve, hides that artefact while keeping more than enough precision for everyday use.
Large and small numbers
When a result is a trillion or more, or smaller than a billionth, it is shown in scientific notation, such as 1.5e+12 for one and a half trillion. The number after e tells you how many places to move the decimal point: to the right for positive values and to the left for negative ones.
Everyday tips
To add a percentage, multiply by one plus the rate: a price of 1,200 plus 10 percent tax is 1,200 × 1.1. To find a share of a bill, divide the total by the number of people. To check a discount, multiply by one minus the rate: 30 percent off 4,500 is 4,500 × 0.7. Writing the steps down first helps avoid order-of-operations surprises on any basic calculator.
Division by zero
Dividing by zero has no meaningful answer in arithmetic, so the calculator shows Error instead of a number. Tap a digit or ac to clear it and start again.
Frequently asked questions
Why does 2 + 3 × 4 give 20?
Like most pocket calculators, it calculates each step in the order you enter it. For 14, calculate 3 × 4 first and then add 2.
Is there a percentage or memory key?
No. The calculator keeps to the four basic operations. Use multiplication for percentages, for example × 1.1 to add 10 percent.
How precise are the results?
Results are rounded to 12 significant digits, which is plenty for shopping, budgeting and most homework.
Is anything saved?
No. Nothing you type is stored or sent anywhere. Reloading the page starts with 0.
Does it work on a computer as well as a phone?
Yes. On a wide screen the calculator is shown at phone width in the middle of the page, and you can click the keys with a mouse or trackpad.
Can I use my keyboard?
The calculator is designed for tapping or clicking the on-screen keys.
What is different from the iPhone app?
The calculator is the same. The iPhone app shows a small banner ad below the keypad; the web version has no ads.
Limitations of the web version
- Four basic operations only, with no percent or memory keys
- Calculates step by step, not in mathematical order of operations
- No calculation history
- Keyboard input is not supported
Phone app
電卓 水色 is also available as an app for phones and tablets: