**Objective**<br />

To evaluate the effect of crowd-figure-pictograms on women’s numeric knowledge about mammography screening in a three-armed parallel randomised controlled trial.<br /><br />

**Results**<br />

552 women were randomised to receive (1) non-numeric information (n = 192), (2) non-numeric and numeric information (n = 186), or (3) non-numeric and numeric information complemented by crowd-figure-pictograms (n = 174). Baseline numeric knowledge was low (control 0.61, numeric 0.66, and pictogram 0.51 on a scale ranging from 0 to 5). Women in the crowd-figure-pictogram group had a larger knowledge increase than women in the numeric group (2.42 vs 2.06, p = .03). Both groups had significant increases in knowledge compared to the control (0.20, p < .001). Providing numeric information in absolute numbers improves knowledge; even more so when crowd-figure-pictograms are added.<br />

Trial registration German Clinical Trials Register DRKS00014736, retrospectively registered 11 May 2018