An optical vital signs sensor (100) is provided, which comprises a PPG sensor (102), a force transducer (130) configured to measure a force applied via the PPG sensor (102) to a skin (1000) of the user and a processing unit (140) configured to extract information regarding a blood volume pulse from the output of the PPG sensor (102) and to map the extracted information to the blood pressure value at a specific force applied to the PPG sensor (102).