Blood Pressure Calculator
AHA category and next steps from systolic and diastolic readings.
What it does
Blood pressure readings pair systolic pressure during heartbeats with diastolic pressure between them. Doctors sort each pair into bands that guide lifestyle advice and medication, so the same two numbers mean the same thing in every clinic.
The tool above takes both numbers in mmHg. It returns the AHA category with the reading repeated and a plain next step for that band.
The default of 135 over 85 lands in Stage 1 hypertension (130 to 139 or 80 to 89). The higher number always decides: a normal systolic with a high diastolic still reads by the diastolic band.
Bands follow the American Heart Association and ACC high blood pressure guideline tables with NHLBI references behind them. When the two numbers fall in different bands, the higher band wins.
How to use
- Sit quietly five minutes, feet flat, back supported.
- Enter the top (systolic) number first.
- Enter the bottom (diastolic) number second.
- Read the category the pair falls in.
- Average several days of readings before acting on one.
Formula
- systolic
- Peak pressure during each heartbeat.
- diastolic
- Resting pressure between beats.
- higher wins
- The worse band of the two decides.
Single readings vary with stress, caffeine, and cuff fit, so categories apply to averages across days, not one excited measurement. Crisis numbers with symptoms mean emergency care, not home tracking.
Worked example
Example: 135 over 85
Systolic 135, diastolic 85.
- Systolic 135 sits in 130 to 139: stage 1 by top.
- Diastolic 85 sits in 80 to 89: stage 1 by bottom.
- Both agree: Stage 1 hypertension.
- Next step: lifestyle changes, medication depends on risk.
- Tool shows Stage 1 hypertension, 135/85 mmHg, lifestyle guidance.
Reference table
| Category | Systolic | Diastolic |
|---|---|---|
| Normal | below 120 | below 80 |
| Elevated | 120 to 129 | below 80 |
| Stage 1 | 130 to 139 | 80 to 89 |
| Stage 2 | 140 or higher | 90 or higher |
| Crisis | above 180 | above 120 |
Limits
- Screening bands, not a diagnosis by itself.
- Single readings swing; averages across days count.
- Cuff size and position shift results substantially.
- Pregnancy and conditions use different targets.
Common mistakes
- Reading one excited number as the final verdict.
- Ignoring a high diastolic because systolic looks fine.
- Measuring over sleeves or with legs crossed.
- Testing right after coffee, exercise, or smoking.
- Stopping medication on one good home reading.
Try it yourself
Quick checks. Answers sit tucked under each question.
118 over 76?
Both below cutoffs: Normal.
145 over 92?
Above 140 or 90: Stage 2 hypertension.
122 over 78?
Systolic 120 to 129 with diastolic below 80: Elevated.
Questions
Is 135 over 85 high?
Yes, Stage 1 by AHA bands (130 to 139 or 80 to 89).
Which number matters more?
Both. The category follows whichever number lands higher.
What is normal blood pressure?
Below 120 systolic and below 80 diastolic.
When is it an emergency?
Above 180 or above 120, with symptoms call 911 immediately.
How should I measure at home?
Rest five minutes seated, feet flat, cuff at heart level, two readings averaged.
Can one reading diagnose?
No. Diagnosis uses averages across visits plus overall risk.