An apparatus for determining blood pressure, comprising: a control unit; and a means for providing pulse wave data representative of a heart beat of a human subject, the subject having a body height, an age, and a gender; wherein the control unit is configured to perform the steps of: receiving the pulse wave data; selecting a portion of the pulse wave data indicative of one or more heart periods; determining a time difference for each/at least one respective heart period of the one or more heart periods; and determining a blood pressure value of the subject based on the time difference, the body height, and/or the age; characterized in that the step of determining the time difference further comprises, for each/at least one respective heart period of the one or more heart periods: - determining a systolic component of the respective heart period; - approximating the systolic component with a first Gaussian function and a second Gaussian function; and - determining the time difference as the time difference between the first and second Gaussian functions; and the step of determining the blood pressure value comprises: - determining a preliminary stiffness index (SI p) based on the body height and the time difference; - determining an adjusted stiffness index (SI a) based on the preliminary stiffness index (SI p) and the age; and - determining the blood pressure value based on the adjusted stiffness index (SI a) and a regression model; wherein the regression model comprises a regression function f SI a g = BP sys, where SI a is the adjusted stiffness index (SI a), g is the gender of the subject, and BP sys is the blood pressure; and wherein determining the blood pressure value comprises determining the blood pressure value based on the regression function; and the regression function comprises a linear function of the type f x = ax + b, wherein a ranges from 1 to 20 mmHg/(m/s) and b ranges from 0 to 80 mmHg, more preferably wherein a ranges from 5 to 15 mmHg/(m/s) and b ranges from 20 to 60 mmHg. a control unit; and a means for providing pulse wave data representative of a heart beat of a human subject, the subject having a body height, an age, and a gender; wherein the control unit is configured to perform the steps of: receiving the pulse wave data; selecting a portion of the pulse wave data indicative of one or more heart periods; determining a time difference for each/at least one respective heart period of the one or more heart periods; and determining a blood pressure value of the subject based on the time difference, the body height, and/or the age; characterized in that receiving the pulse wave data; selecting a portion of the pulse wave data indicative of one or more heart periods; determining a time difference for each/at least one respective heart period of the one or more heart periods; and determining a blood pressure value of the subject based on the time difference, the body height, and/or the age; the step of determining the time difference further comprises, for each/at least one respective heart period of the one or more heart periods: - determining a systolic component of the respective heart period; - approximating the systolic component with a first Gaussian function and a second Gaussian function; and - determining the time difference as the time difference between the first and second Gaussian functions; and - determining a systolic component of the respective heart period; - approximating the systolic component with a first Gaussian function and a second Gaussian function; and - determining the time difference as the time difference between the first and second Gaussian functions; and the step of determining the blood pressure value comprises: - determining a preliminary stiffness index (SI p) based on the body height and the time difference; - determining an adjusted stiffness index (SI a) based on the preliminary stiffness index (SI p) and the age; and - determining the blood pressure value based on the adjusted stiffness index (SI a) and a regression model; wherein the regression model comprises a regression function f SI a g = BP sys, where SI a is the adjusted stiffness index (SI a), g is the gender of the subject, and BP sys is the blood pressure; and wherein determining the blood pressure value comprises determining the blood pressure value based on the regression function; and - determining a preliminary stiffness index (SI p) based on the body height and the time difference; - determining an adjusted stiffness index (SI a) based on the preliminary stiffness index (SI p) and the age; and - determining the blood pressure value based on the adjusted stiffness index (SI a) and a regression model; wherein the regression model comprises a regression function f SI a g = BP sys, the regression function comprises a linear function of the type f x = ax + b, wherein a ranges from 1 to 20 mmHg/(m/s) and b ranges from 0 to 80 mmHg, more preferably wherein a ranges from 5 to 15 mmHg/(m/s) and b ranges from 20 to 60 mmHg.