Respiratory Calculators

78 calculators & risk scores

Browse 78 Respiratory clinical calculators and risk scores used in everyday UK practice. Every tool runs entirely in your browser — enter the values and get instant scoring, colour-coded interpretation bands and a link to the underlying guideline or publication. ClinCalc Pro is free, needs no sign-up, and is built for working clinicians.

These respiratory tools span ABG Interpretation, Asthma, Pneumonia, COPD, Pleural Disease, Spirometry and more.

A-a Oxygen Gradient

Calculates the alveolar-arterial oxygen gradient to assess for V/Q mismatch and diffusion defects.
PEFR % Predicted

Calculates peak expiratory flow rate as percentage of predicted to classify asthma severity.
Pneumonia Severity Index (PSI/PORT)

Predicts 30-day mortality in community-acquired pneumonia. Simplified from the full Fine/PORT score.
BODE Index

Predicts mortality in COPD using BMI, airflow obstruction, dyspnoea, and exercise capacity.
mMRC Dyspnoea Scale

Grades breathlessness severity to guide COPD management and pulmonary rehabilitation referral.
Light's Criteria for Pleural Effusion

Distinguishes exudative from transudative pleural effusions using protein and LDH ratios.
FEV₁/FVC Ratio (Airflow Obstruction)

Interprets spirometry FEV₁/FVC ratio to classify airflow obstruction severity per GOLD criteria.
Pulmonary Embolism Severity Index (PESI)

Predicts 30-day mortality in acute PE to guide disposition (inpatient vs outpatient management). Validated in multiple large cohorts.
Simplified PESI (sPESI)

Simplified version of PESI using 6 binary variables to predict 30-day mortality after acute PE. Easier to calculate bedside than the original PESI.
Hestia Criteria for Outpatient PE Treatment

11 clinical criteria to determine if a patient with acute PE is safe for outpatient (home) treatment. If ANY criterion is met, outpatient treatment is NOT recommended.
YEARS Algorithm for PE Diagnosis

Stepwise algorithm combining 3 clinical items with D-dimer to exclude PE. Uses lower D-dimer threshold (500 μg/L) when ≥1 YEARS item present, higher threshold (1000 μg/L) when no YEARS items.
Padua Prediction Score for VTE Risk

Estimates VTE risk in hospitalised medical patients to guide thromboprophylaxis decisions.
STOP-BANG Score for Obstructive Sleep Apnoea

Screens for moderate-to-severe obstructive sleep apnoea (OSA) using 8 binary questions. Used pre-operatively and in outpatient settings.
Winters' Formula for Metabolic Acidosis Compensation

Predicts the expected compensatory pCO₂ for a primary metabolic acidosis. A measured pCO₂ outside this range indicates a co-existing respiratory disorder.
PaO₂/FiO₂ Ratio (P/F Ratio)

Calculates the ratio of arterial oxygen tension to inspired oxygen fraction. Used to classify severity of hypoxaemic respiratory failure and diagnose ARDS per Berlin criteria.
CRB-65 Score for Community Pneumonia

Simplified pneumonia severity score not requiring urea measurement. Used in community and primary care settings to guide admission decisions in CAP.
SMART-COP Score for Pneumonia Severity

Predicts need for intensive respiratory or vasopressor support (IRVS) in community-acquired pneumonia. Identifies patients who may require ICU-level care.
RAPID Score for Pleural Infection

Predicts 3-month mortality in patients with pleural infection (empyema/complicated parapneumonic effusion) to guide management intensity. Validated in the MIST2 trial cohort.
ARISCAT Score for Post-operative Pulmonary Complications

Predicts risk of postoperative pulmonary complications (atelectasis, respiratory failure, pleural effusion, pneumonia, pneumothorax, bronchospasm) in non-cardiac surgery patients.
Arterial Oxygen Content (CaO₂)

Calculates total arterial oxygen content — oxygen bound to haemoglobin plus dissolved in plasma. Used to assess oxygen delivery (DO₂ = CaO₂ × CO × 10).
Age-Adjusted D-Dimer Threshold for PE

Calculates the age-adjusted D-dimer threshold for excluding PE in patients over 50. Reduces unnecessary CTPA in elderly patients with low-to-moderate pre-test probability. Formula: age × 10 μg/L.
GOLD COPD Classification

GOLD 2023 ABCD assessment tool for COPD combining symptom burden (CAT/mMRC) and exacerbation history to guide therapy.
Berlin Criteria for ARDS

2012 Berlin Definition of ARDS. Classifies severity by PaO₂/FiO₂ ratio with PEEP ≥ 5 cmH₂O.
COPD Assessment Test (CAT)

8-item patient-reported outcome measure quantifying COPD symptom impact on daily life. Validated for GOLD ABCD grouping.
Fleischner Society Guidelines — Pulmonary Nodules

2017 Fleischner Society guidelines for management of incidentally discovered pulmonary nodules on CT in adults ≥ 35 years.
Mayo Clinic Solitary Pulmonary Nodule Malignancy Risk

Estimates probability of malignancy in a solitary pulmonary nodule (SPN) using 6 independent predictors. Validated in multiple cohorts.
ABG Interpretation Guide

Stepwise interpretation of arterial blood gas. Identifies primary acid-base disorder and degree of compensation.
Wells' Criteria for Pulmonary Embolism

Pre-test probability score for pulmonary embolism. Guides decisions regarding D-dimer testing and CT pulmonary angiography (CTPA) in suspected PE.
Revised Geneva Score for Pulmonary Embolism

Revised Geneva Score for pre-test probability of pulmonary embolism. Fully objective score using only clinical and laboratory variables — no physician gestalt required.
Bova Score for Pulmonary Embolism Complications

Risk stratification tool for intermediate-risk (haemodynamically stable) PE patients. Identifies those at risk of PE-related complications and death within 30 days.
CURB-65 Score for Community-Acquired Pneumonia

Severity scoring for community-acquired pneumonia (CAP). Guides decision between outpatient, inpatient, and ICU care. British Thoracic Society standard score.
Hamilton Score for DVT Clinical Probability

Predicts probability of deep vein thrombosis (DVT) in outpatients. An alternative to the Wells DVT score with similar performance.
DECAF Score for Acute Exacerbation of COPD

Dyspnoea, Eosinopenia, Consolidation, Acidaemia, and Atrial Fibrillation (DECAF) score predicts in-hospital mortality in acute exacerbations of COPD.
BAP-65 Score for Acute Exacerbation of COPD

BUN, altered mental status, pulse ≥109, age ≥65 (BAP-65) score predicts in-hospital mortality and need for mechanical ventilation in AECOPD.
MuLBSTA Score for Viral Pneumonia Mortality

Predicts 90-day mortality in viral pneumonia. Validated in influenza and non-influenza viral pneumonias. MuLBSTA = Multilobar infiltrates, Lymphopenia, Bacterial co-infection, Smoking, Tumour, Age.
Ottawa COPD Risk Scale

Predicts 30-day serious adverse events (SAEs) in patients with AECOPD presenting to the emergency department. Score ≥1 associated with significantly increased SAE risk.
ROX Index for Intubation after HFNC

Predicts failure of high-flow nasal cannula (HFNC) in patients with acute hypoxaemic respiratory failure. ROX <3.85 at 12h predicts HFNC failure and need for intubation.
Rapid Shallow Breathing Index (RSBI)

Predicts successful extubation in mechanically ventilated patients. RSBI = respiratory rate / tidal volume (L). Values <105 predict weaning success.
GAP Index for Idiopathic Pulmonary Fibrosis

Gender, Age, Physiology (GAP) index predicts 1, 2, and 3-year mortality in idiopathic pulmonary fibrosis (IPF) using clinical and physiological variables.
du Bois Score for IPF Mortality

Predicts 1-year mortality in IPF from a single clinical visit using age, hospitalisation history, %predicted FVC, and 24-week FVC change. du Bois risk score ranges 0–100.
LENT Prognostic Score for Malignant Pleural Effusion

Predicts survival in patients with malignant pleural effusion (MPE). Scores LDH, ECOG status, NLR, and tumour type (LENT) to guide management decisions.
Clinical Pulmonary Infection Score (CPIS) for VAP

Diagnoses ventilator-associated pneumonia (VAP) using clinical, radiological, and microbiological criteria. Score >6 suggests VAP.
Static Lung Compliance Calculation

Calculates static lung compliance (Cstat) in mechanically ventilated patients. Reduced compliance (<60 mL/cmH₂O) indicates stiff lungs (ARDS, pneumonia, pulmonary oedema).
SpO₂/FiO₂ (S/F) Ratio

Non-invasive surrogate for the PaO₂/FiO₂ ratio using pulse oximetry. Avoids arterial blood gas requirement. S/F ratio <315 correlates with ARDS (P/F <300).
Brock University Lung Cancer Malignancy Score

Predicts malignancy probability in pulmonary nodules found on CT screening. Validated for nodules 6–30 mm. Used alongside Fleischner and BTS guidelines.
DRIP Score for Drug-Resistant Pneumonia

Drug Resistance in Pneumonia (DRIP) score identifies patients with community-acquired pneumonia at risk of drug-resistant pathogen infection (excluding MRSA/Pseudomonas HCAP criteria). Score ≥4 indicates high-risk.
Murray Score for Acute Lung Injury

Lung Injury Score (LIS) assesses severity of acute lung injury (ALI). Score ≥2.5 indicates severe ALI / ARDS. Used historically to assess ECMO candidacy.
MACOCHA Score for Difficult Intubation in ICU

Predicts difficult intubation in critically ill patients in the ICU. MACOCHA = Mallampati III or IV, Apnoea/OSA, reduced mobility of Cervical spine, Opening mouth, Coma, Hypoxaemia, non-Anaesthesiologist.
HACOR Score for NIV Failure Risk

Heart rate, Acidosis, Consciousness, Oxygenation, and Respiratory rate (HACOR) score predicts the risk of non-invasive ventilation (NIV) failure and need for intubation in patients with acute respiratory failure. Assessed at 1-2 hours after NIV initiation. Score above 5 predicts NIV failure with 72% sensitivity and 89% specificity. Validated by Liu et al. 2017 in 449 patients.
PROMISE Score for Malignant Pleural Effusion Prognosis

Prognostic score for patients with malignant pleural effusion (MPE). Predicts 3-month mortality. Based on LENT score variables plus Performance status. Score 0-7: score 0-1 = low risk (median survival above 12 months); 2-4 = intermediate; 5-7 = high risk (median survival 2 months). Helps guide intervention choices (indwelling pleural catheter vs talc pleurodesis). From Bibby et al. 2018.
SCAP Score for Severe Community-Acquired Pneumonia

Severe Community-Acquired Pneumonia (SCAP) score for predicting adverse outcomes (need for ICU, mechanical ventilation, death) in hospitalised CAP patients. 8-variable score. High score predicts severe outcome. Validated by Espana et al. 2006. Can be used alongside PSI/PORT and CURB-65 for ICU triage.
Pulmonary Embolism Severity Index (PESI) -- Full Version

Full PESI score predicts 30-day mortality in acute pulmonary embolism. Classifies patients into 5 risk classes (I-V) based on age, sex, cancer, heart failure, COPD, heart rate, systolic BP, respiratory rate, temperature, mental status, and O2 saturation. Risk Class I-II (very low/low) may be suitable for outpatient treatment with DOAC. Validated in 11,000+ patients. Note: simplified PESI (sPESI) also available in this app.
4-Level Pulmonary Embolism Clinical Probability Score (4PEPS)

Novel 4-level clinical probability score for pulmonary embolism that includes age and directly classifies patients into unlikely/low/intermediate/high PE probability. Developed by Roy et al. 2021 as an improvement over Wells and revised Geneva scores in the age of D-dimer adjustment. Designed to reduce unnecessary CTPA ordering. Validated in 1,746 patients.
Lung Injury Prediction Score (LIPS)

Lung Injury Prediction Score (LIPS) identifies patients at risk for developing Acute Lung Injury (ALI) / ARDS early in the hospital course (before ALI is established). Enables early preventive strategies (lung-protective ventilation, restrictive fluid strategy, avoidance of blood products). Validated by Gajic et al. 2011 in 5,584 patients. Score above 4 = high risk (ALI development rate 18% vs 3% for low risk).
RESP Score for Respiratory ECMO Survival Prediction

Respiratory ECMO Survival Prediction (RESP) score. Predicts in-hospital survival for patients receiving veno-venous ECMO (VV-ECMO) for acute respiratory failure. Based on 12 pre-ECMO variables. Score -22 to +15; Class I (score above 5) = 92% survival; Class V (score below -5) = 18% survival. Developed by Schmidt et al. 2014 from the ELSO registry of 2,355 patients. Used to guide ECMO candidacy decisions.
ARISCAT Score for Postoperative Pulmonary Complications

Assesses risk of postoperative pulmonary complications (PPC) in adults undergoing surgery. Guides preoperative optimisation and perioperative respiratory monitoring.
Berlin Criteria for Acute Respiratory Distress Syndrome (ARDS)

2012 Berlin Definition of ARDS. Classifies ARDS severity (mild/moderate/severe) based on PaO₂/FiO₂ ratio while on PEEP ≥5 cmH₂O. Replaces the American-European Consensus Conference definition.
CRB-65 Score for Community-Acquired Pneumonia

CRB-65 score assesses severity of community-acquired pneumonia (CAP) in primary care or ED settings (no blood tests required). Guides hospital admission decisions.
CURB-65 Score for Community-Acquired Pneumonia

CURB-65 score predicts 30-day mortality in community-acquired pneumonia (CAP). Hospital-based version of CRB-65; requires blood urea measurement. Standard tool for CAP severity assessment.
Brock University Lung Nodule Malignancy Model

Estimates probability of malignancy in incidental pulmonary nodules detected on CT. Based on the Pan-Canadian Early Detection of Lung Cancer Study. Guides surveillance and biopsy decisions.
DRIP Score for Drug-Resistant Pneumonia

Drug Resistance in Pneumonia (DRIP) score. Predicts risk of drug-resistant pneumonia pathogens to guide empirical antibiotic selection in CAP and HCAP patients.
GOLD COPD Assessment (Spirometry + Symptom-Exacerbation)

Global Initiative for Obstructive Lung Disease (GOLD) 2023 COPD classification. Grades spirometric severity (GOLD 1–4) and ABCD group based on symptom burden (mMRC/CAT) and exacerbation history.
Gupta Postoperative Pneumonia Risk Score

Predicts risk of postoperative pneumonia requiring antibiotics or respiratory support within 30 days of non-cardiac surgery. Developed from the American College of Surgeons NSQIP database.
DELTA-P Score for SVC Syndrome in Tumour

Dutch-English LEMS Tumour Association Prediction (DELTA-P) Score. Predicts prognosis in superior vena cava (SVC) syndrome from lung malignancy and guides treatment decisions.
EPIPHANY Index for PE in Cancer

Predicts clinical outcome of pulmonary embolism (PE) in cancer patients. Guides management intensity (outpatient vs admission vs ICU) and anticoagulation decisions.
FEV1 % Predicted Calculator

Calculates the predicted FEV1 based on age, sex, and height using GLI-2012 reference equations. Used to interpret spirometry and classify COPD/restriction severity.
Expected Peak Expiratory Flow (PEF) Calculator

Estimates predicted peak expiratory flow (PEF) based on sex, age, and height using Nunn-Gregg or ECCS reference equations. Used to assess asthma severity (% predicted PEF).
Altitude-Adjusted PERC Rule for PE

Modified Pulmonary Embolism Rule-out Criteria (PERC) adjusted for altitude. At high altitudes (>4000 ft/1220 m), physiological SpO₂ is lower, so the cut-off is adjusted from 95% to 90% to maintain specificity.
Asthma Severity Classification (GINA)

GINA (Global Initiative for Asthma) 2023 severity and control classification. Guides step-up/step-down of inhaled therapy from Step 1 (PRN SABA) to Step 5 (biologic therapy).
ROX Index (Risk of Intubation on HFNC)

Predicts failure of high-flow nasal cannula (HFNC) oxygen therapy and need for intubation in acute hypoxaemic respiratory failure.
NIV Failure Predictor Score

Predicts likelihood of non-invasive ventilation (NIV) failure in acute hypercapnic respiratory failure (AHRF) and COPD exacerbations.
Oxygen Delivery (DO2) Calculator

Calculates oxygen delivery (DO2) to tissues from cardiac output, haemoglobin, and oxygen saturation. Normal DO2: 950-1150 mL/min.
CO2 Retention Risk in COPD (High-Flow O2)

Estimates risk of hypercapnic respiratory failure when administering supplemental oxygen in COPD patients. Guides target SpO2 selection (88-92%).
Plethysmographic Variability Index (PVI) / Fluid Responsiveness

Non-invasive assessment of fluid responsiveness using respiratory variation in pulse oximetry plethysmographic waveform amplitude.
Maximum Voluntary Ventilation (MVV) / Breathing Reserve

Estimates maximum voluntary ventilation and breathing reserve index from FEV1. Used in pre-operative respiratory assessment.
Physiological Dead Space (Bohr Equation)

Calculates physiological dead space fraction using the Bohr-Enghoff equation. Elevated VD/VT (>0.6) predicts poor outcomes in ARDS.
Asthma Control Test (ACT)

Patient-completed 5-question test for asthma control over past 4 weeks. Score <=19 = not well controlled; score <=15 = very poorly controlled.
Oxygen Saturation Target Selection

Selects appropriate SpO2 target range based on clinical condition. Prevents both hypoxia and oxygen toxicity (hyperoxia). Based on BTS Oxygen Guidelines.