Hazard Risk Priority Number (RPN) Calculator
ANA›Life Services Authority›National Calculator Authority›Hazard Risk Priority Number (RPN) Calculator
.calc-container { max-width: 640px; margin: 2rem 0; padding: 1.5rem; background: #fff; border: 1px solid #ddd; border-radius: 8px; box-shadow: 0 1px 3px rgba(0,0,0,0.06); font-family: system-ui, -apple-system, sans-serif; } .calc-container h3 { font-family: Georgia, serif; font-size: 1.15rem; color: #1a1a1a; margin-bottom: 1rem; padding-bottom: 0.5rem; border-bottom: 2px solid var(--ac, #3d5a80); } .calc-row { display: flex; align-items: center; gap: 0.75rem; margin-bottom: 0.75rem; flex-wrap: wrap; } .calc-row label { min-width: 160px; font-size: 0.9rem; color: #333; font-weight: 500; } .calc-row input[type="number"], .calc-row select { flex: 1; min-width: 120px; max-width: 200px; padding: 0.5rem 0.6rem; border: 1px solid #ccc; border-radius: 4px; font-size: 0.9rem; font-family: system-ui, sans-serif; color: #1a1a1a; background: #fafaf8; } .calc-row input:focus, .calc-row select:focus { outline: none; border-color: var(--ac, #3d5a80); box-shadow: 0 0 0 2px rgba(26,74,138,0.12); } .calc-row .unit { font-size: 0.82rem; color: #888; min-width: 30px; } .calc-btn { display: inline-block; margin-top: 0.5rem; padding: 0.55rem 1.5rem; background: var(--ac, #3d5a80); color: #fff; border: none; border-radius: 4px; font-size: 0.9rem; font-weight: 600; cursor: pointer; font-family: system-ui, sans-serif; } .calc-btn:hover { opacity: 0.9; } .calc-result { margin-top: 1.25rem; padding: 1rem 1.25rem; background: #f0f6fc; border-left: 3px solid var(--ac, #3d5a80); border-radius: 0 6px 6px 0; display: none; } .calc-result.visible { display: block; } .calc-result-label { font-size: 0.78rem; text-transform: uppercase; letter-spacing: 0.06em; color: #666; margin-bottom: 0.25rem; } .calc-result-value { font-size: 1.6rem; font-weight: 700; color: var(--ac, #3d5a80); } .calc-result-detail { font-size: 0.85rem; color: #555; margin-top: 0.5rem; line-height: 1.5; } .calc-note { margin-top: 1rem; font-size: 0.8rem; color: #888; font-style: italic; } .calc-grid { display: grid; grid-template-columns: 1fr 1fr; gap: 0.75rem; margin-top: 0.75rem; } .calc-grid-item { padding: 0.6rem 0.8rem; background: #f8f9fa; border-radius: 4px; border: 1px solid #eee; } .calc-grid-item .label { font-size: 0.75rem; color: #888; text-transform: uppercase; letter-spacing: 0.04em; } .calc-grid-item .value { font-size: 1.1rem; font-weight: 600; color: #1a1a1a; } @media (max-width: 720px) { .calc-row { flex-direction: column; align-items: flex-start; gap: 0.3rem; } .calc-row label { min-width: auto; } .calc-row input[type="number"], .calc-row select { max-width: 100%; width: 100%; } .calc-grid { grid-template-columns: 1fr; } } .calc-chart { margin: 1rem 0; text-align: center; } .calc-chart svg { max-width: 100%; height: auto; } .calc-chart-legend { display: flex; flex-wrap: wrap; justify-content: center; gap: 0.6rem 1.2rem; margin-top: 0.6rem; font-size: 0.8rem; color: #555; } .calc-chart-legend span { display: inline-flex; align-items: center; gap: 0.3rem; } .calc-chart-legend i { display: inline-block; width: 10px; height: 10px; border-radius: 2px; font-style: normal; } .calc-related { max-width: 640px; margin: 2rem 0 1rem; padding: 1.25rem 1.5rem; background: #f8f9fa; border: 1px solid #e8e8e8; border-radius: 8px; } .calc-related h3 { font-family: Georgia, serif; font-size: 1rem; color: #1a1a1a; margin: 0 0 0.75rem; padding-bottom: 0.4rem; border-bottom: 2px solid var(--ac, #3d5a80); } .calc-related-list { list-style: none; padding: 0; margin: 0 0 0.75rem; display: grid; grid-template-columns: 1fr 1fr; gap: 0.4rem 1.5rem; } .calc-related-list li a { font-size: 0.88rem; color: var(--ac, #3d5a80); text-decoration: none; } .calc-related-list li a:hover { text-decoration: underline; } .calc-browse-all { margin: 0.5rem 0 0; font-size: 0.9rem; font-weight: 600; } .calc-browse-all a { color: var(--ac, #3d5a80); text-decoration: none; } .calc-browse-all a:hover { text-decoration: underline; } @media (max-width: 720px) { .calc-related-list { grid-template-columns: 1fr; } }
Hazard Risk Priority Number (RPN) Calculator
Calculate the Hazard Risk Priority Number (RPN) used in Failure Mode and Effects Analysis (FMEA) and hazard risk assessments. RPN helps prioritize risks by combining Severity, Probability of Occurrence, and Detectability scores.
Severity (S) (1–10)
1 = No effect | 10 = Catastrophic
Probability of Occurrence (P) (1–10)
1 = Extremely unlikely | 10 = Almost certain
Detectability (D) (1–10)
1 = Almost certain to detect | 10 = Undetectable
Calculate RPN
function hazValidate(el, min, max) { var v = parseFloat(el.value); if (el.value === "") { el.style.borderColor = ""; return; } if (isNaN(v) || v max || !Number.isInteger(v)) { el.style.borderColor = "#c0392b"; } else { el.style.borderColor = "#27ae60"; } }
function hazGetInt(id, min, max) { var el = document.getElementById(id); var v = parseFloat(el.value); if (el.value === "" || isNaN(v) || v max || !Number.isInteger(v)) return null; return v; }
function hazRiskLabel(rpn) { if (rpn >= 200) return { label: "Critical Risk", color: "#c0392b" }; if (rpn >= 125) return { label: "High Risk", color: "#e67e22" }; if (rpn >= 50) return { label: "Moderate Risk", color: "#f1c40f" }; if (rpn >= 10) return { label: "Low Risk", color: "#27ae60" }; return { label: "Negligible Risk", color: "#2ecc71" }; }
function hazCalc() { var errEl = document.getElementById("haz-error"); errEl.style.display = "none"; errEl.textContent = "";
var S = hazGetInt("haz-severity", 1, 10); var P = hazGetInt("haz-probability", 1, 10); var D = hazGetInt("haz-detectability", 1, 10);
var errors = []; if (S === null) errors.push("Severity must be a whole number between 1 and 10."); if (P === null) errors.push("Probability must be a whole number between 1 and 10."); if (D === null) errors.push("Detectability must be a whole number between 1 and 10.");
if (errors.length > 0) { errEl.innerHTML = errors.join(""); errEl.style.display = "block"; document.getElementById("haz-result").style.display = "none"; return; }
// Core formula: RPN = S × P × D var RPN = S * P * D; var risk = hazRiskLabel(RPN);
document.getElementById("haz-rpn-value").textContent = "RPN = " + RPN; document.getElementById("haz-rpn-value").style.color = risk.color;
var riskEl = document.getElementById("haz-risk-level"); riskEl.textContent = "Risk Level: " + risk.label; riskEl.style.color = risk.color;
document.getElementById("haz-breakdown").innerHTML = "Severity (S) = " + S + " × " + "Probability (P) = " + P + " × " + "Detectability (D) = " + D + " = " + RPN + "";
document.getElementById("haz-result").style.display = "block"; }
#### Formula
RPN = S × P × D
- S (Severity): Rates the seriousness of the hazard's effect on a scale of 1–10.
- P (Probability of Occurrence): Rates the likelihood that the hazard will occur on a scale of 1–10.
- D (Detectability): Rates how difficult it is to detect the hazard before harm occurs on a scale of 1–10 (10 = hardest to detect).
- RPN range: 1 (minimum risk) to 1,000 (maximum risk).
Risk Thresholds (common industry guidance):
- RPN ≥ 200 → Critical Risk — Immediate action required
- RPN 125–199 → High Risk — Priority corrective action
- RPN 50–124 → Moderate Risk — Action plan recommended
- RPN 10–49 → Low Risk — Monitor and review
- RPN 1–9 → Negligible Risk — Acceptable, document only
#### Assumptions & References
- The RPN method is defined in IEC 60812:2018 (Failure modes and effects analysis) and widely used in ISO 14971 (medical devices), AIAG FMEA standards (automotive), and MIL-STD-882 (system safety).
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