Scientific Calculator Online (Casio Style)

A scientific calculator online that works like a Casio

This scientific calculator online is laid out like the Casio fx-991 that most students use in class: the same two-line display, a SHIFT key for second functions, degree and radian modes, Ans, memory and fraction results. If you know your handheld calculator, you already know how to use this one. It’s free, needs no download and works on phones as well as desktops.

Toolz Directory isn’t affiliated with Casio. We simply built the keypad the way people are used to, so it’s a good stand-in when your own calculator is at home or its battery is flat.

What you can calculate with this scientific calculator online

• Trigonometry: sin, cos and tan, their inverses with SHIFT, and hyperbolic versions with hyp. Switch between degrees, radians and gradians with DRG.
• Powers and roots: x², x³, any power with xʸ, square and cube roots, and reciprocals with x⁻¹.
• Logs and exponentials: log (base 10), ln, 10ˣ and eˣ.
• Counting: factorials (x!), permutations (nPr) and combinations (nCr).
• Everyday extras: percentages, absolute value, π and e, scientific notation with ×10ˣ, and ENG mode for engineering notation.

How to use the online Casio-style calculator

1. Type the expression the way you would write it, for example 2sin(30)+√(16). You can tap the keys or use your keyboard.
2. Press = or Enter. The expression stays on the top line and the answer appears below it, just like on an fx-991.
3. Carry on from the answer. Press an operator straight after a result and the calculator starts with Ans, so ÷3 divides the last answer by three.
4. Press S⇔D to switch a result between a decimal and a fraction, for example 0.75 and 3⌟4.
5. Click any line in the history to reuse it. Your history, memory and angle mode are remembered next time you visit.

Degrees or radians?

The small letter at the top of the display shows the angle unit: D for degrees, R for radians, G for gradians. This is the most common reason for a “wrong” trig answer. In degree mode, sin(30) is 0.5. In radian mode the same keys give −0.988, because 30 radians is a very different angle. School geometry usually uses degrees, while calculus and physics formulas often assume radians.

Casio calculator online: keys at a glance

Key	What it does	With SHIFT
x²	Square	x³, cube
√	Square root	∛, cube root
log	Base-10 logarithm	10ˣ
ln	Natural logarithm	eˣ
sin, cos, tan	Trig functions	sin⁻¹, cos⁻¹, tan⁻¹
x⁻¹	Reciprocal	x!, factorial
nCr	Combinations	nPr, permutations
M+	Add the answer to memory	M−, subtract from memory

Errors on the scientific calculator and what they mean

Like a real Casio, this scientific calculator online shows Math ERROR when the question has no answer, such as dividing by zero, the log of a negative number or tan(90°). It shows Syntax ERROR when the expression can’t be read, usually because of a missing number or an unclosed bracket. Press DEL to fix it, or AC to start again.

For checking exam practice, keep in mind that this is a calculator, not a solver. It won’t show working steps. If you’re preparing for an exam, check which calculator models your exam board allows, as online calculators are rarely permitted in the exam room.

Related calculators

For quick percentage questions use the Percentage Calculator, and for converting units between systems try the Unit Converter. If you need an exact copy of a specific model, Casio sells official emulator software for its calculators.

Frequently asked questions

Is this the official Casio calculator online?

No. Casio sells emulator software for its own calculators. This is an independent scientific calculator online with a Casio-style layout, free to use in any browser.

How do I get fractions like on a Casio?

Calculate as normal, then press S⇔D. If the answer can be written as a simple fraction, it appears as 3⌟4 style notation. Press S⇔D again to go back to the decimal.

Why is my sin answer wrong?

Check the angle unit at the top of the display. Press DRG until it shows D for degrees if your question uses degrees.

Can I use my keyboard with the Casio calculator online?

Yes. Type numbers, operators and function names such as sin(30) or log(100), press Enter for the answer and Esc to clear.

Does the scientific calculator online work on a phone?

Yes. The keypad resizes to fit the screen, and the phone keyboard stays hidden so the calculator keys are easy to tap.