Math Keyboard for iPhone: Fractions, Symbols & LaTeX

The built-in iOS keyboard covers only a handful of math characters, so for real notation you add a specialized keyboard. Sigmakey installs as a system-wide keyboard extension with a full math layout — sum, integral, root, Greek letters, arrows, and inequality signs — available in any app where you can type. You switch to it with the globe key like any other keyboard.

Typing a fraction as plain text like 3/4 loses the structure and gets ambiguous fast in longer expressions. Sigmakey has a fraction template key that creates a real numerator-over-denominator box pair in the equation field. You fill each box, nest more structures inside if needed, and the fraction stays editable as a unit.

Yes. Sigmakey builds the equation visually on a two-dimensional keyboard and serializes it to clean LaTeX source when you insert it. You do not have to remember command names — the box structure you typed becomes the corresponding LaTeX expression, ready to paste into a document, editor, or forum that renders it.

LaTeX is the standard markup language for mathematical notation, used in academic papers, theses, and many online course systems. Writing it by hand on a phone keyboard is slow and error-prone because of the backslash commands and braces. Sigmakey generates the LaTeX for you from the equation you typed visually, so the output is correct without memorizing syntax.

That requires the editor to treat the equation as a structure rather than a string — which is exactly what most symbol keyboards do not do. In Sigmakey, every fraction, exponent, and root is a navigable box with real hit-testing, so tapping the denominator places the caret in the denominator. You fix the one part that is wrong and leave the rest untouched.

Yes. Sigmakey includes the Greek alphabet on its layout, and the symbol search lets you type a name — theta, pi, lambda — to get the glyph immediately. Frequently used letters can be pinned to a favorites row so they are always one tap away.

Plain-text chat cannot display LaTeX, so Sigmakey offers a Unicode best-effort mode that converts your equation into readable characters — superscripts, fraction slashes, and proper symbols — that survive as ordinary text. For anything too complex for Unicode, you can insert a rendered image of the typeset equation instead. The keyboard remembers which mode each app needs.

Yes. Sigmakey typesets the expression on-device and produces a rendered image you can insert wherever pictures are accepted. That is the most faithful option for apps that support neither LaTeX nor rich Unicode, and it keeps complex layouts like matrices looking exactly as typed.

iOS runs third-party keyboards in a restricted sandbox, and a keyboard without Full Access cannot send anything off the device. Sigmakey keeps Full Access off by default, performs all typesetting locally, makes no network calls, and has no account. What you type stays on your phone.

Open Settings, go to General, then Keyboard, then Keyboards, and tap Add New Keyboard to select the one you installed. After that, the globe key on the keyboard cycles to it in any app. Sigmakey shows this as a guided checklist on first launch so setup takes under a minute.

Yes. Sigmakey has a matrix template that lays out rows and columns as a grid of editable boxes, so you fill cells rather than hand-typing brackets and separators. The finished matrix serializes to proper LaTeX or renders as an image, depending on the output mode you choose.

Completely. The layout engine, the symbol search, and the LaTeX, Unicode, and image serializers all run on the device with no network dependency. It behaves identically in airplane mode, in a lecture hall with no signal, or anywhere else.