Blood Pressure Zone Calculator

How the zones are determined (with visuals)

This calculator classifies blood pressure using two widely quoted frameworks: ACC/AHA (US, clinic/office) and NICE NG136 (UK). Both consider Systolic (SBP) and Diastolic (DBP), and both use a “higher category wins” rule: if SBP and DBP land in different zones, the final category is the more severe of the two.

Core thresholds at a glance

• ACC/AHA (US, clinic/office): Normal <120/<80; Elevated 120–129 and <80; Stage 1 130–139 or 80–89; Stage 2 ≥140 or ≥90; Hypertensive crisis flag at ≥180 and/or ≥120.
• NICE NG136 (UK): Clinic normal <140/<90; Stage 1 typically 140–159 or 90–99 (confirm with HBPM/ABPM average ≥135/85); Stage 2 ≥160 or ≥100 (or HBPM/ABPM average ≥150/95). For home/ambulatory averages, “normal” is <135/<85.

Worked examples (how the visual maps to real numbers)

• Example A — 118/76 mmHg: US → Normal; UK clinic → Normal; UK home/ABPM (if averaged) → Normal. Both SBP and DBP fall in the green segment.
• Example B — 126/78 mmHg: US → Elevated (blue: SBP 120–129 with DBP <80); UK clinic → Normal (still <140/90). For home/ABPM averages this would remain “normal” (<135/85).
• Example C — 132/86 mmHg: US → Stage 1 (amber: SBP 130–139 or DBP 80–89). UK clinic → Below 140/90 (not staged in clinic), but if this is a home/ABPM average, DBP ≥85 places it in Stage 1.
• Example D — 166/92 mmHg: US → Stage 2 (SBP ≥140). UK clinic → Stage 2 (SBP ≥160). On the bar this sits well inside the orange/red region.
• Example E — 182/88 mmHg: US → Hypertensive crisis (SBP ≥180). UK clinic → Severe threshold (≥180 or ≥120). This is in the far red segment and warrants urgent attention, especially with concerning symptoms.
• Example F — 128/94 mmHg: US → Stage 2 (DBP ≥90 drives the higher category). UK clinic → Stage 1 (DBP 90–99); UK home/ABPM average → Stage 1 (DBP ≥85 but <95). The “higher category wins” rule explains why US shows a more severe label here.

Why two systems?

The US scheme emphasizes earlier categorization inside the clinic. The UK approach uses clinic readings for initial triage but recommends confirmation with home (HBPM) or ambulatory (ABPM) averages using slightly lower cut-offs (135/85 and 150/95). That’s why your category can differ by context. When in doubt, take several measurements, rest for 5 minutes before measuring, and consider averaging home/ambulatory readings for a clearer picture. This tool is for education only and does not replace professional medical advice.