Make 18 with four 4s

The classic four fours puzzle: build an expression from exactly four 4s that equals 18. 18 cannot be made with + - × ÷ alone (the solver checked every expression) — you will need to stick 4s together (like 44) or use decimals (like .4).

Solutions using only + - × ÷

No expression made of four plain 4s and + - × ÷ reaches 18 — the solver checked every possible expression.

Solutions with concatenation and decimals

.4 + .4 × 44 = 18
.4 + 4 × 4.4 = 18
4 + 4 + 4 / .4 = 18
(.4 + 4) × 4 + .4 = 18

Solutions with square roots, factorials, exponents

4! + 4 - 4 / .4 = 18
4 + 4! - 4 / .4 = 18
(4 × 4! - 4!) / 4 = 18
4! - (4 - 4 / 4)! = 18
4! - (4 / .4 - 4) = 18

…and 342 more at this tier.

351 distinct solutions found in total, after removing trivial rearrangements.

Make 17 with four 4s · Make 19 with four 4s

The Number Lab

Same idea, different constraints: four 9s, four 4s, or any four digits you like.

Four Nines — the daily puzzle
Four Nines solver — every target, solved
Four Fours — the 1881 original
Four Fours solver — including the impossible five
Make 24 solver — any four digits
Today's 24 — one new hand a day

Read up on the 1881 original, pick another number in the solver, or find more free math games.