Apparatus for determining blood pressure of a subject, comprising: - a sensor signal input configured to obtain an arterial pulse wave sensor signal of the subject, - a feature extraction unit configured to extract multiple different features from the obtained arterial pulse wave sensor signal, thereby providing individual extracted features and/or groups of extracted features - an estimation unit configured to determine multiple blood pressure estimation values for the individual extracted features and/or groups of extracted features and to determine the subject's blood pressure from said multiple blood pressure estimation values, - a calibration unit configured to calibrate the estimation unit based on blood pressure reference measurements, wherein said calibration unit is configured to determine calibration values for determining said multiple blood pressure estimation values for the individual extracted features and/or groups of extracted features by said estimation unit by fitting a modelled relation between an extracted feature or group of extracted features and blood pressure to the actually extracted feature value or group of extracted feature values and the blood pressure reference measurements, and wherein said estimation unit is configured to determine the multiple blood pressure estimation values for the individual extracted features and/or groups of extracted features using the modelled relation and the determined calibration values, and - a calibration trigger unit configured to trigger calibration by the calibration unit if the multiple blood pressure estimation values diverge more than a divergence limit, divergence being a measure for the difference between the multiple blood pressure estimation values. - a sensor signal input configured to obtain an arterial pulse wave sensor signal of the subject, - a feature extraction unit configured to extract multiple different features from the obtained arterial pulse wave sensor signal, thereby providing individual extracted features and/or groups of extracted features - an estimation unit configured to determine multiple blood pressure estimation values for the individual extracted features and/or groups of extracted features and to determine the subject's blood pressure from said multiple blood pressure estimation values, - a calibration unit configured to calibrate the estimation unit based on blood pressure reference measurements, wherein said calibration unit is configured to determine calibration values for determining said multiple blood pressure estimation values for the individual extracted features and/or groups of extracted features by said estimation unit by fitting a modelled relation between an extracted feature or group of extracted features and blood pressure to the actually extracted feature value or group of extracted feature values and the blood pressure reference measurements, and wherein said estimation unit is configured to determine the multiple blood pressure estimation values for the individual extracted features and/or groups of extracted features using the modelled relation and the determined calibration values, and wherein said calibration unit is configured to determine calibration values for determining said multiple blood pressure estimation values for the individual extracted features and/or groups of extracted features by said estimation unit by fitting a modelled relation between an extracted feature or group of extracted features and blood pressure to the actually extracted feature value or group of extracted feature values and the blood pressure reference measurements, and wherein said estimation unit is configured to determine the multiple blood pressure estimation values for the individual extracted features and/or groups of extracted features using the modelled relation and the determined calibration values, and - a calibration trigger unit configured to trigger calibration by the calibration unit if the multiple blood pressure estimation values diverge more than a divergence limit, divergence being a measure for the difference between the multiple blood pressure estimation values.