Combination Sum Calculator — Find Numbers That Add Up to a Target [2026]

Yes, by default each candidate number can be used unlimited times. You can toggle "Use each number once" to restrict each number to a single use, which is useful for finding exact matches in a list of unique values like invoices or transactions.

For performance in the browser, we recommend keeping the candidate set under 20 numbers and the target sum under 1000. Larger inputs may produce thousands of combinations and take longer to compute.

The calculator uses a backtracking algorithm with pruning. It sorts the candidates first, then systematically explores all possible combinations while skipping branches that cannot possibly reach the target. This is the same approach used in computer science interviews and competitive programming.

Large inputs can produce millions of combinations. The 500-combination limit keeps the tool responsive in your browser. For most practical problems (accounting, puzzles, resource allocation), the complete solution set is well under this limit.

The calculator is designed for positive integers. Negative numbers create infinite combinations (you could keep adding and subtracting). If you need negative number support, filter your results based on additional constraints.

Combinations ignore order — [2, 3, 5] and [5, 3, 2] are the same combination. Permutations treat different orderings as distinct results. This calculator finds combinations only, which is what most practical use cases need.