OpenR1-Math-220k is a large-scale dataset for mathematical reasoning. It consists of 220k math problems with two to four reasoning traces generated by DeepSeek R1 for problems from NuminaMath 1.5. The traces were verified using Math Verify for most samples and Llama-3.3-70B-Instruct as a judge for 12% of the samples, and each problem contains at least one reasoning trace with a correct answer. The dataset consists of two splits: - default with 94k problems and that achieves the best performance after SFT. - extended with 131k samples where we add data sources like cnk12. This provides more reasoning traces, but we found that the performance after SFT to be lower than the default subset…