Play Crossmath Online Free: History, Rules & Strategy

A grid of empty squares, a scattering of plus, minus, times and divide signs, and a pile of digits waiting to be slotted into place — every row and column a tiny equation that has to come out exactly right. That is Crossmath: part crossword, part mental arithmetic, all satisfying click when the last number falls. If you love the deductive snap of a logic grid but want a little arithmetic flavor, this is your puzzle.

The history of Crossmath

Crossmath belongs to a long family of "arithmetic crossword" or cross-sums puzzles, and its roots reach back to 1950. That year Jacob E. Funk, a Canadian writer for Dell Magazines, created the number-cross puzzle "Cross Sums" — the ancestor that later became a worldwide hit in Japan as Kakuro, popularized by Nikoli's Maki Kaji from 1980 (source).

The specific operator-based "Cross-Math" format — placing the digits 1 through 9 so that several horizontal and vertical equations are simultaneously true — was developed and popularized as a competition puzzle by American mathematician Erich Friedman, a longtime professor of mathematics at Stetson University. His Cross-Math puzzles have appeared in Games and World of Puzzles magazines and in the U.S. Puzzle Championship since the late 1990s (source). Friedman is a prolific recreational-puzzle constructor whose work has shaped the modern competition scene (source).

The puzzle reached a mass international audience between roughly 2019 and 2023 through free mobile apps branded "Crossmath" and "Crossmath - Math Puzzle Games," published by studios such as AppCubic and Arithmo and distributed on the Apple App Store and Google Play. These apps standardized the now-common rules of dragging digits into 5×5 up to 9×9 grids to satisfy every equation at once (source). Today the word "Crossmath" covers both these mobile games and the printable math-crossword workbooks aimed at students and adults.

How to play Crossmath

The rules are quick to learn, and you can open a fresh grid on our free Crossmath board in seconds.

1. Read the grid. The board is an interlocking set of cells crossed by operator symbols (+, −, ×, ÷) and equals signs, forming a horizontal equation along each row and a vertical equation down each column.
2. Know your number pool. You are given a set of digits to place — commonly 1 through 9, each used once — which you drag or type into the empty cells.
3. Make every equation true. Each row reads as an equation (for example, 8 × 3 − 4 = 20) and each column does too. Your goal is to place numbers so that all of them hold simultaneously.
4. Obey order of operations. Inside each equation, do multiplication and division before addition and subtraction — just like in school math.
5. Attack the most constrained clue first. Find the equation with the fewest possible digit combinations (often a multiplication or division with a very large or very small result) and lock those cells in.
6. Cascade across intersections. Every digit you place also lives in a crossing equation, so a confirmed cell instantly narrows the perpendicular line. Follow that chain.
7. Check and finish. The puzzle is solved when every row and column equation is true and every required number has been used.

Do you need to be good at math to play Crossmath?

No — Crossmath only uses basic arithmetic you already know; the real challenge is the logical deduction of which digit fits where, not the difficulty of the sums themselves.

Strategy & tips

Crossmath rewards smart sequencing far more than fast calculation. These tactics keep a grid flowing:

• Start where choices are fewest. A clue like "× = 72" has very few digit pairs that work, so it pins cells fast. A clue like "+ = 12" has many, so skip it for now.
• Use the intersections. Because each cell belongs to both a row and a column equation, solving one line hands you free constraints on the other.
• Track what is used. When each digit appears only once, cross off numbers as you place them to shrink the pool and reveal forced cells.
• Respect precedence. Re-read each filled line as the game will evaluate it — multiply and divide first — so a chain like 6 + 2 × 3 equals 12, not 24.
• Work elimination, not guesswork. If a cell has only one digit that keeps both its equations valid, place it; a well-made puzzle never forces a blind guess.

Mathematician Erich Friedman, the constructor who popularized the modern Cross-Math format, notes that because each digit 1–9 is placed exactly once and every horizontal and vertical equation must hold at the same time, the strongest opening strategy is to attack the most constrained equation first — multiplication or division clues with extreme results, since those admit the fewest digit combinations and quickly fix cells that cascade into the rest of the grid via order of operations (source).

If you enjoy that deductive-arithmetic blend, you will likely love our siblings: try the classic cross-sums of Kakuro, the cage-arithmetic of Calcudoku, or the math-flavored Killer Sudoku.

What is the difference between Crossmath and Kakuro?

In Kakuro you only add digits to hit a target sum with no repeats, while Crossmath uses all four operations (+, −, ×, ÷) inside full equations that must each evaluate correctly under order of operations.

Watch a video tutorial

Seeing the digits drag into place makes the format click instantly. A clear primer is the "Crossmath - Math Puzzle Games App Walk Through" on the TopGames app-walkthrough channel:

Want more reps? There is also a full "Crossmath - Math Puzzle Game" playlist walking through many solved boards at different sizes.

Ready to solve?

The best way to learn Crossmath is to lock in that first constrained equation yourself and feel the rest of the grid cascade. Jump into a fresh board and play Crossmath free online — no download, no signup, just you and the numbers. Craving more variety afterward? Stretch your logic with Sudoku or our rotating daily puzzles, and see how fast you can make every equation true.