NHS Blood Pressure Calculator
This independent UK blood pressure calculator explains how to calculate an average from repeated home readings using current NHS and NICE guidance. It is not an official NHS diagnostic service.
Home blood pressure average method
Record systolic (top number) and diastolic (bottom number) readings separately. Add all included systolic readings and divide by the number of readings. Repeat for the diastolic values.
NICE diagnostic home-monitoring method: take 2 consecutive seated readings at least 1 minute apart, twice daily, ideally morning and evening, for at least 4 days and ideally 7 days. Discard the first day’s measurements and average all remaining measurements.
Home threshold: NHS guidance generally considers 135/85 mmHg or higher at home to be high. NICE uses an HBPM average of 135/85 mmHg or higher, alongside a raised clinic reading, to confirm hypertension.
What is a blood pressure average calculator?
Blood pressure varies during the day, so repeated readings can give a more useful picture than one isolated result. Systolic pressure is the top number and diastolic pressure is the bottom number.
How to measure blood pressure at home
Sit upright with your back supported, feet flat on the floor and arm supported. Relax and do not talk during the measurement. The NHS advises taking another reading a few minutes after the first. Follow any monitoring schedule given by your healthcare professional.
Formula
Average systolic = sum of included systolic readings / number of included readings.
Average diastolic = sum of included diastolic readings / number of included readings.
Worked example
For included readings of 132/82, 136/84, 134/80 and 130/82, average systolic = 532 / 4 = 133 mmHg. Average diastolic = 328 / 4 = 82 mmHg. The average is 133/82 mmHg.
Understanding blood pressure readings
The NHS says blood pressure is usually considered high at 140/90 mmHg or higher when checked by a healthcare professional, or 135/85 mmHg or higher when checked at home. Blood pressure below 90/60 mmHg is considered low. Individual treatment targets can differ with age, health conditions and clinical advice.
Important limitations
A single high reading is not the same as a diagnosis. This page is for adults and should not be used to diagnose symptoms, pregnancy, children, or situations where a clinician has provided different instructions. Seek urgent medical help for emergency symptoms such as persistent chest pain or signs of stroke regardless of the numbers shown.
Authoritative sources
- NICE NG136: Hypertension in adults
- NHS: Blood pressure test
- NHS: High blood pressure
- NHS: Low blood pressure
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FAQs
How do I calculate average blood pressure at home?
Average systolic readings separately from diastolic readings. For NICE diagnostic home monitoring, discard the first day’s measurements and average the remaining measurements.
What home blood pressure average is considered high?
The NHS generally considers 135/85 mmHg or higher at home to be high.
How many readings should I take?
NICE recommends two consecutive readings at least one minute apart, twice daily, for at least 4 days and ideally 7 days when home monitoring is used to confirm hypertension.
Is one high reading enough to diagnose hypertension?
No. Diagnosis normally requires appropriate repeat, ambulatory or home monitoring according to clinical guidance.
Medical disclaimer: This independent page is for general information only and does not replace advice from a GP, pharmacist, nurse or other qualified healthcare professional.