Re-Pair [1] is an effective grammar-based compression scheme achieving strong compression rates in practice. Let n, σ, and d be the text length, alphabet size, and dictionary size of the final grammar, respectively. In their original paper, the authors show how to compute the Re-Pair grammar in expected linear time and 5n + 4σ 2 + 4d + √ n words of working space on top of the text. In this work, we propose two algorithms improving on the space of their original solution. Our model assumes a memory word of log 2 n bits and a re-writable input text composed by n such words. Our first algorithm runs in expected O(n/ ) time and uses (1 + )n + √ n words of space on top of the text for any parameter 0 < ≤ 1 chosen in advance. Our second algorithm runs in expected O(n log n) time and improves the space to n + √ n words.