Four basic operations, smart percent, and an engineering mode with powers, roots, logarithms and trigonometry
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Engineering mode
About This Tool
An online calculator for everyday and engineering math: the four basic operations, percentages, powers and roots, logarithms, factorial and trigonometry. The result updates as you type, before you press equals. No install, no signup.
The most common use is discounts and final prices: "250000 minus 30%" gives the price after the discount, and "200 plus 15%" gives the price with a 15 percent increase. It also covers invoices and sales tax, checking an instalment or interest figure, splitting a bill between friends, and school-level math and physics practice, so you never have to reach for your phone calculator.
Full keyboard support is built in, Persian digits are accepted too, and results are shown with thousands separators so you do not misread long numbers. Engineering mode starts collapsed to keep the keypad simple and opens with one click. None of your calculations leave your device.
Frequently Asked Questions
How does the percent key work?
It takes its meaning from the operator next to it. 200 + 15% gives 230, a 15 percent increase. 200 − 15% gives 170, a 15 percent discount. 20% × 500 gives 100, twenty percent of 500. A percentage on its own, such as 25%, is simply 0.25.
How do I calculate a price after a discount?
Enter the original price, press minus, then the discount and the percent key. For 30 percent off 250, type 250 − 30% and the result 175 appears. For step-by-step percentage work, the percentage calculator is a better fit.
How do I add sales tax?
Type the amount, then plus, then the tax rate and the percent key. For example 480 + 10% gives the total with 10 percent tax. If you only want the tax itself, compute it as 10% × 480.
How do I open engineering mode, and what is in it?
Click "Engineering mode" below the number keypad. It holds the trigonometric functions, parentheses, natural and base-10 logarithms, roots, square, arbitrary powers, pi, e, factorial, reciprocal and the Ans key. Whether it is open is remembered, so it stays open next time.
What does the INV key do?
It flips the keys to their inverses: sin to sin⁻¹, cos to cos⁻¹, tan to tan⁻¹, ln to eˣ, log to 10ˣ, square root to cube root, square to cube and reciprocal to absolute value. Press it again to switch everything back.
Do the trigonometric functions use degrees or radians?
Degrees by default, so sin 30 is 0.5. Use the DEG and RAD buttons inside engineering mode to switch, and your choice is saved for next time.
How do I calculate powers and roots?
Use x² for a square and xʸ for any exponent: 2, then xʸ, then 10 gives 1024. Use √ for a square root, and press INV to turn it into ∛ for a cube root. Any other root works as a fractional exponent, for example 27 to the power of one third is 3.
Can I use the keyboard?
Yes. Type digits and operators directly, press Enter for the result, Backspace to delete the last character and Esc to start over. Persian digits are accepted as well.
In what order are operations performed?
Standard math order: parentheses first, then exponents, then multiplication and division, and finally addition and subtraction. So 2 + 3 × 4 is 14, not 20. Use the parentheses in engineering mode when you need a different order.
How do I reuse a result in the next calculation?
After pressing equals, typing an operator continues from that result. In engineering mode the Ans key inserts the last answer anywhere in an expression. To take the result elsewhere use the copy button next to the display; it only appears once an actual calculation has been made.
It says "Incomplete expression" or "Unclosed parenthesis". What is wrong?
The expression is not finished: an operator is left hanging at the end, or a parenthesis was opened and never closed. Delete the last character with Backspace or close the parenthesis. The other messages are just as direct: division by zero, logarithm needs a positive number, square root of a negative number is undefined, and factorial needs a whole non-negative number.
Why are there gaps between the digits of the result?
Those are thousands separators, so long numbers are quick to read and you do not miscount zeros. They have no effect on the math, and copying gives you the plain number without them.
Are my calculations stored anywhere?
No. Nothing you calculate leaves your device; only two small settings (degrees or radians, and whether engineering mode is open) are remembered in this browser.
