Readability of text is generally believed to be connected to sentence length. Most studies on readability are based on visual reading. Less is known about text readability for users relying on screen readers, such as users who are blind. This study therefore set out to investigate the effect of sentence length on the readability of web texts accessed using screen readers. A controlled withinsubjects experiment was performed with twenty-one participants. Participants used a screen reader to read five texts with different sentence lengths. The participants' comprehension and perceived workload were measured. The findings reveal that there is a significant effect of sentence length and most participants exhibit the highest comprehension and lowest workload with sentences comprising 16-20 words. Implications of these results are that web content providers should strive for sentence length of 16-20 words to maximize readability.