🧮 Scientific Calculator

DEG · RAD · GRAD, memory keys, and a tape you can edit

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⚡ 10-second version

A calculator that doesn't lose your work. Every entry lands on an editable tape at tooladda.online/scientific-calculator.html — so when you mistype step four of a nine-step calculation, you fix step four instead of starting again.

Important

Install it once and it works with the network off. On a phone in an exam hall, on a plane, or in a lab with no Wi-Fi, a calculator that needs a connection is not a calculator.

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⚠️ The two mistakes that ruin real answers

1. Wrong angle mode — the silent wrong answer

This is the single most common source of "the calculator is broken". It isn't; it's in radians when you meant degrees.

You type	In DEG	In RAD
sin(30)	0.5 ✅	-0.988031624... ❌
tan(90)	error / ∞	-1.9952...

Both answers are correct arithmetic. Only one answers your question. The current mode is shown permanently in the display here, because a mode indicator you have to go looking for is a mode indicator you'll forget.

2. Floating-point reality

Every calculator on every computer stores numbers in binary IEEE 754 doubles, and some decimals simply don't exist in binary:

0.1 + 0.2        →  0.30000000000000004
0.3 − 0.1        →  0.19999999999999998
sin(π)           →  1.2246467991473532e-16     (not exactly 0)
tan(89.9999°)    →  572957.795...              (blowing up toward ∞)

This is not a bug in this tool — it's how binary floating point works, everywhere, including Excel and your phone. Knowing it means you stop chasing a 4 in the seventeenth decimal place and start rounding at the precision your problem actually has.

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🧭 How the tape changes things

flowchart LR
    A["⌨️ Keys or<br/>keyboard input"] --> B["Expression parser"]
    B --> C["Angle mode<br/>DEG · RAD · GRAD"]
    C --> D["Evaluate"]
    D --> E["📜 Tape entry<br/>(editable)"]
    E -->|"fix a step"| B
    E --> F["Memory<br/>M+ M− MR MC"]
    E --> G["📋 Copy / export"]

    style A fill:#0ea5e9,stroke:#0369a1,color:#fff
    style C fill:#f59e0b,stroke:#b45309,color:#fff
    style E fill:#075985,stroke:#0c4a6e,color:#fff
    style G fill:#22c55e,stroke:#15803d,color:#fff

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That loop back from the tape into the parser is the feature. A normal calculator has no way to draw that arrow.

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✨ What's inside

📜 Editable calculation tape Every step is kept and every step is editable. Correct one line and everything downstream recomputes — the way a spreadsheet behaves, in a calculator's form factor.	📐 Full function set sin cos tan and inverses, log ln exp, powers, roots, n!, nCr / nPr, π and e, reciprocals, percentages.
🎚️ DEG / RAD / GRAD Always visible, one tap to switch. GRAD included for surveying and some engineering coursework where 400 gradians to a turn is still standard.	🧠 Memory keys M+ M− MR MC behaving the way a physical scientific calculator behaves — no relearning.
⌨️ Real keyboard support Type expressions with the number row and operators. On a laptop, typing beats clicking buttons with a mouse every time.	✈️ Installable PWA Add to home screen, open with no connection. No ads, no popups, no cookie banner between you and an answer.

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🛠️ Who reaches for it

Situation	Why this one
🎓 Students doing physics or maths homework	The tape shows your working — which is half the marks.
🏗️ Engineers checking a quick figure	DEG/RAD/GRAD without hunting through a settings menu.
🧪 Lab work	Offline on a bench machine with no internet access.
💰 Anyone doing multi-step money maths	Fix an early step without re-entering eight numbers.
📱 Phone users who don't want another app	Install the page instead of installing an APK full of ads.
🧑‍🏫 Teachers demonstrating on a projector	Large, readable display and visible history for the class to follow.

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📖 Getting the most out of it

1.  Open    →  tooladda.online/scientific-calculator.html
2.  Check   →  the angle mode indicator BEFORE any trig
3.  Type    →  use the keyboard, not the mouse
4.  Edit    →  click a tape line to correct it, don't restart
5.  Install →  browser menu → Install / Add to Home Screen (for offline)

▶ Open it now — tooladda.online/scientific-calculator.html

Tip

Round at the end, not at every step. Rounding intermediate values is how a chain of correct operations produces a visibly wrong final answer — and the editable tape lets you keep full precision until the last line.

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❓ FAQ

Is it free and ad-free?

Free, and no interstitial ads or popups. No signup either.

Why does 0.1 + 0.2 not give exactly 0.3?

Binary floating point can't represent 0.1 or 0.2 exactly, so the sum lands a hair above 0.3. Every mainstream calculator and spreadsheet has this property; some hide it by rounding the display. Knowing about it is more useful than hiding it.

Why is sin(π) not zero?

Because π itself is stored as a finite approximation, so you're taking the sine of *almost* π. The result is about 1.22 × 10⁻¹⁶ — mathematically zero for any practical purpose.

What is GRAD and do I need it?

Gradians: 400 to a full turn instead of 360 degrees. It shows up in surveying and some European engineering syllabi. If you've never needed it, you don't.

Does it work offline?

Yes. Install it as a PWA and it opens and computes with no connection.

Can I use my keyboard?

Yes — digits, operators, parentheses, Enter to evaluate, Escape to clear.

Can I copy the whole calculation out?

Yes, the tape can be copied — useful for pasting your working into homework or a report.

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🔬 Under the hood

• Vanilla JavaScript expression parser — no eval(), so a pasted expression can't execute code.
• IEEE 754 doubles, like every other software calculator; display precision is handled separately from stored precision.
• Service worker + web manifest for genuine offline use.
• Covered by unit tests, because a calculator that's occasionally wrong is worse than no calculator.

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🧰 Related ToolAdda tools

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Check the mode. Keep the tape. Get the answer.

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