About SciKey

Features

• Type expressions as written — Handles operator precedence, brackets and implied multiplication (2π, 3(4+5)), and previews the result live as you type. Works with both the keypad and your keyboard.
• Scientific functions — Trig, inverse trig and hyperbolic functions (DEG/RAD/GRAD), log, ln and logₐ, eˣ and 10ˣ, square and n-th roots, xʸ, n!, nPr, nCr, |x|, mod, round, floor, ceil, gcd and lcm.
• Constants — Call π, e, φ and 20 CODATA 2022 physical constants (speed of light, Planck constant, Avogadro constant, electron mass and more) by name.
• Memory, variables, history — M+, M−, MR and MC independent memory, Ans, variables x, y and z (STO), and your last 50 calculations (tap to reload).
• Display formats — Normal (NORM), scientific (SCI) and engineering (ENG) notation, 6 to 15 significant digits, plus fraction, multiple-of-π and binary/octal/hex display.
• Privacy — All calculations happen inside your browser; history and settings are stored only in your device's localStorage.

How to use

1. First check the angle unit with the DEG/RAD/GRAD buttons at the top (it changes trig results).
2. Type an expression with the keypad or keyboard, e.g. 2sin(30)+√(16). The result is previewed below as you type.
3. Press = or Enter to confirm. The result is added to the history and stored in Ans. Pressing an operator such as × next continues the calculation from Ans.
4. The 2nd key enters the secondary functions printed small above the keys (sin⁻¹, 10ˣ, eˣ, x³, ∛, φ, floor). The hyp key turns sin, cos and tan into hyperbolic functions.
5. To keep a result, press STO and then x, y or z, or add it to memory with M+.
6. Change the display format (NORM, SCI, ENG) and significant digits at the top of the screen. Fraction, multiple-of-π and base representations appear under the result when available.

Accuracy and floating-point handling

All calculations use JavaScript's IEEE 754 double-precision (64-bit) floating point, which gives about 15 to 17 significant digits. Expressions are parsed by our own recursive-descent parser without eval, and function values were checked against 1,786 reference values from mpmath (40 digits), all within a relative error of 2×10⁻¹⁴.

1. 0.1 + 0.2 — binary floating point cannot represent 0.1 exactly, so the internal value is 0.30000000000000004. SciKey rounds to your significant-digit setting (12 by default) and shows 0.3. Handheld scientific calculators hide the error the same way, computing with 15 internal digits and showing 10. The internal value stays in Ans unchanged.
2. Trig functions in DEG and GRAD modes — the argument is reduced exactly by 360° (400 gon), and multiples of 90° (100 gon) return exact values: sin(180°) = 0, cos(90°) = 0, and tan(90°) is 'undefined'.
3. sin(π) in RAD mode — the π you type is an approximation that differs from the true π by about 1.22×10⁻¹⁶, so the raw sine is 1.22×10⁻¹⁶. When the argument matches an integer multiple of π within a relative error of 10⁻¹³, sin is corrected to 0; at odd multiples of π/2, cos is corrected to 0 and tan(π/2) is treated as 'undefined'.
4. Range — results with an absolute value above about 1.797×10³⁰⁸ give an overflow error (e.g. 171!). Operations outside the domain (√−1, log 0, asin 2, division by zero) are math errors; complex numbers are not supported.
5. Integer precision — integers above 2⁵³ (about 9×10¹⁵) may not be exact to the last unit. Factorials from 23! upward are approximations.

Frequently asked questions