Free Health Tools & Calculators
Privacy-first calculators and reference guides — nothing you enter is stored. Work in metric or imperial. Educational only; for advice, talk to a verified doctor.
Book a consultationGeraClinic’s free tools fall into three groups: privacy-first health calculators (BMI, calorie, due-date and more), educational clinical-score calculators that reproduce published decision rules, and UK registration & relocation tools for internationally-qualified clinicians. Planning a move to the UK? Start with the free work in the NHS from overseas guide, then the Health & Care Worker visa checker.
Body & weight
BMI Calculator
Body Mass Index (BMI) is a simple screening number calculated from your height and weight. This free calculator works in metric and imperial units and shows where your BMI falls on the WHO reference chart.
Ideal Weight
Estimate a healthy weight range for your height using the WHO BMI range plus classic clinical reference formulas (Devine, Robinson, Miller, Hamwi). Works in kg and lb.
Body Fat %
Estimate your body-fat percentage using the U.S. Navy circumference method from a few tape measurements. An estimate for tracking trends — not a clinical body-composition scan.
Waist-to-Height
Waist-to-height ratio (WHtR) is a simple measure of central body fat. Keeping your waist under half your height is a widely used general guideline. Works in cm and inches.
Nutrition & fitness
BMR / Calorie Needs
Your Basal Metabolic Rate (BMR) is the energy your body uses at rest; your Total Daily Energy Expenditure (TDEE) adds your activity. This calculator uses the Mifflin-St Jeor equation to estimate daily calorie needs.
Water Intake
Estimate a general daily water target based on your body weight and activity. A practical rule-of-thumb to support healthy hydration — your needs change with climate, health, and pregnancy.
Heart Rate Zones
Estimate your maximum heart rate and the five training zones (from recovery to maximum effort) based on your age, to guide cardio exercise intensity.
Heart & metabolic
Blood Pressure
Enter a blood-pressure reading to see where it falls on the ACC/AHA reference chart (normal, elevated, hypertension stages). This explains the categories — it does not diagnose high blood pressure.
A1C ↔ Glucose
Convert between HbA1c (%) and estimated average glucose (eAG) using the ADAG formula, and between mg/dL and mmol/L. A reference converter for understanding your own lab results.
Glucose Units
Convert blood glucose readings between mg/dL (used in the US) and mmol/L (used in the UK, EU and most of the world). A simple reference converter.
Pregnancy & fertility
Due Date
Estimate your pregnancy due date and current week from the first day of your last menstrual period (LMP), using Naegele’s rule. An estimate — your clinician’s dating scan is the authoritative date.
Ovulation
Estimate your most fertile days and likely ovulation date from your last period and average cycle length. An estimate based on cycle averages — fertility varies cycle to cycle.
Children
When to see a doctor
Fever — see a doctor?
General guidance on the fever situations that usually warrant medical attention — for adults, children and infants. Educational only; if you are worried, speak to a doctor.
Chest pain — see a doctor?
Chest pain can have many causes, some of them emergencies. This page explains the warning signs that mean you should seek urgent or emergency care, and when to book a consultation.
Headache — see a doctor?
Most headaches are not dangerous, but some patterns are red flags. This page explains the headache warning signs that warrant urgent assessment and when to book a consultation.
Medication reference
UK registration & relocation tools
Free, email-gated tools for internationally-qualified doctors, nurses, pharmacists, dentists and allied health professionals planning a move to the UK — visa eligibility, salary thresholds, NHS pay and relocation costs, all sourced from GOV.UK and NHS Employers.
Health & Care Worker Visa Checker
Check your eligibility for the UK Health and Care Worker visa in a few questions.
Immigration Salary List / Shortage Occupation Checker
Check whether your role is on the UK Immigration Salary List and eligible for sponsorship.
UK Registration Readiness Checker
A personalised document and exam checklist for your regulator (GMC, NMC, GPhC, GDC, HCPC).
NHS Pay (Agenda for Change) Calculator
Estimate your NHS Agenda for Change band and take-home pay, including HCAS.
UK Relocation Cost Estimator
Estimate the up-front cost of moving to the UK — visa, exams, flights and first month.
UK Registration Checklist
The full document and exam checklist for doctors, nurses, pharmacists, dentists and allied health.
Clinical scores & decision tools
Educational reference calculators that reproduce published clinical decision rules and risk scores from inputs you already have. They do not diagnose or recommend treatment — always confirm with a clinician.
Cardiology
CHA₂DS₂-VASc
The CHA₂DS₂-VASc score estimates annual stroke risk in people with non-valvular atrial fibrillation, to help guide anticoagulation decisions. It scores eight clinical factors from 0 to 9 points.
HAS-BLED
The HAS-BLED score estimates the 1-year risk of major bleeding in people with atrial fibrillation who are considered for, or taking, anticoagulation. It scores seven factors from 0 to 9 points.
Mean Arterial Pressure
Mean arterial pressure (MAP) is the average pressure in the arteries over one cardiac cycle and reflects perfusion of the organs. It is estimated as diastolic pressure plus one-third of the pulse pressure: MAP = (systolic + 2 × diastolic) ÷ 3.
HEART
The HEART score risk-stratifies emergency-department patients with chest pain for major adverse cardiac events (MACE) over the next six weeks. It scores five elements — History, ECG, Age, Risk factors and Troponin — each 0, 1 or 2 points, for a total of 0 to 10.
TIMI (UA/NSTEMI)
The TIMI risk score for unstable angina / non-ST-elevation MI sums seven equally-weighted clinical predictors (0–7) to estimate the 14-day risk of death, new or recurrent myocardial infarction, or severe recurrent ischaemia needing urgent revascularisation.
Sgarbossa
The Sgarbossa criteria help diagnose acute myocardial infarction when a left bundle branch block obscures the usual ST changes. Three ECG findings carry weighted points — concordant ST elevation (5), concordant ST depression in V1–V3 (3), and discordant ST elevation of 5 mm or more (2). A total of 3 or more is highly specific for acute MI.
CHADS₂
The CHADS₂ score estimates annual stroke risk in atrial fibrillation from five factors (congestive heart failure, hypertension, age ≥75, diabetes and prior stroke/TIA), on a scale of 0 to 6.
QTc (Bazett & Fridericia)
The corrected QT interval (QTc) adjusts the measured QT for heart rate. This tool reports both the Bazett (QT ÷ √RR) and Fridericia (QT ÷ ∛RR) corrections, with sex-specific prolongation thresholds.
Pulmonary & sepsis
Wells DVT
The Wells score for deep vein thrombosis (DVT) estimates the pre-test probability of a leg DVT from nine clinical criteria, helping decide whether a D-dimer or ultrasound is the right next test.
Wells PE
The Wells score for pulmonary embolism (PE) estimates the pre-test probability of a PE from seven clinical criteria, to help select between D-dimer testing and CT pulmonary angiography.
CURB-65
CURB-65 estimates 30-day mortality risk in community-acquired pneumonia from five factors (Confusion, Urea, Respiratory rate, Blood pressure, age ≥65) to help decide on hospital admission.
qSOFA
qSOFA is a rapid bedside score (3 criteria: altered mentation, systolic BP ≤100 mmHg, respiratory rate ≥22) that flags patients with suspected infection at higher risk of poor outcomes.
Padua VTE
The Padua Prediction Score estimates the risk of venous thromboembolism (VTE) in hospitalised medical patients from eleven clinical factors, to decide whether thromboprophylaxis is warranted. A score of 4 or more indicates high risk.
A–a gradient
The alveolar–arterial (A–a) oxygen gradient is the difference between the calculated alveolar oxygen tension (from the alveolar gas equation) and the measured arterial PaO₂. It helps localise the cause of hypoxaemia. The normal gradient widens with age, approximately (age ÷ 4) + 4 mmHg on room air.
Revised Geneva
The revised Geneva score estimates the pre-test probability of pulmonary embolism from purely clinical variables — age, previous DVT/PE, recent surgery or fracture, active malignancy, unilateral limb pain, haemoptysis, heart rate, and leg-vein tenderness with oedema — without needing arterial blood gases or a chest X-ray.
Light’s Criteria
Light’s criteria separate an exudative from a transudative pleural effusion using paired pleural-fluid and serum values. The effusion is an exudate if any one of three conditions is met: a protein ratio over 0.5, an LDH ratio over 0.6, or a pleural LDH above two-thirds of the upper limit of normal serum LDH.
CRB-65
CRB-65 estimates 30-day mortality in community-acquired pneumonia from four bedside factors — Confusion, Respiratory rate ≥30, low Blood pressure and age ≥65 — without needing blood tests, to help decide on hospital referral.
PESI
The Pulmonary Embolism Severity Index (PESI) estimates 30-day mortality in acute pulmonary embolism from age plus ten clinical variables, sorting patients into risk classes I–V.
sPESI
The simplified Pulmonary Embolism Severity Index (sPESI) estimates 30-day mortality in acute pulmonary embolism from six equally-weighted criteria; a score of 0 identifies low-risk patients who may suit outpatient care.
Kidney & renal
eGFR (CKD-EPI 2021)
Estimates glomerular filtration rate (eGFR) from serum creatinine, age and sex using the race-free 2021 CKD-EPI creatinine equation now recommended by the National Kidney Foundation and ASN.
Creatinine Clearance
Estimates creatinine clearance using the Cockcroft-Gault equation — still widely used for renal drug-dosing decisions — from age, weight, sex and serum creatinine.
FENa
The fractional excretion of sodium (FENa) is the percentage of filtered sodium that is excreted in the urine, calculated from paired urine and plasma sodium and creatinine. In oliguric acute kidney injury, a FENa under 1% conventionally suggests a pre-renal cause and over 2% suggests intrinsic renal disease such as acute tubular necrosis.
Liver
MELD 3.0
The MELD 3.0 score estimates 90-day mortality in chronic liver disease and is used by UNOS/OPTN for liver-transplant allocation. It uses creatinine, bilirubin, INR, sodium, albumin and sex.
Child-Pugh
The Child-Pugh score grades the severity of chronic liver disease (cirrhosis) into class A, B or C from five factors: bilirubin, albumin, INR, ascites and hepatic encephalopathy.
FIB-4
The FIB-4 index estimates the likelihood of advanced liver fibrosis from age, AST, ALT and platelet count, helping decide who needs further fibrosis assessment. It is widely used to rule out advanced fibrosis in fatty liver disease and viral hepatitis.
Maddrey DF
Maddrey’s Discriminant Function (DF) estimates short-term mortality in alcoholic hepatitis from prothrombin time and total bilirubin: DF = 4.6 × (patient PT − control PT) + total bilirubin (mg/dL). A DF of 32 or more defines severe disease and is the usual threshold for considering corticosteroids.
MELD-Na
The MELD-Na score adds serum sodium to the original Model for End-Stage Liver Disease to estimate short-term mortality in chronic liver disease. It uses bilirubin, INR, creatinine and sodium, and was used by UNOS/OPTN for U.S. liver-transplant allocation from 2016 until MELD 3.0 replaced it in 2023.
SAAG
The serum-ascites albumin gradient (SAAG) is the serum albumin minus the ascitic-fluid albumin, measured on samples taken the same day. A gradient of 1.1 g/dL or more indicates portal hypertension (such as cirrhosis or heart failure) with about 97% accuracy, while under 1.1 g/dL points to a non-portal cause.
APRI
The AST-to-Platelet Ratio Index (APRI) is a non-invasive estimate of liver fibrosis: (AST ÷ AST upper limit of normal × 100) ÷ platelet count. Lower values make significant fibrosis unlikely; higher values make it likely.
NAFLD Fibrosis Score
The NAFLD Fibrosis Score (NFS) estimates the likelihood of advanced liver fibrosis in non-alcoholic fatty liver disease from age, BMI, glucose status, AST/ALT, platelets and albumin.
Neurology
Glasgow Coma Scale
The Glasgow Coma Scale (GCS) scores level of consciousness from eye, verbal and motor responses, giving a total from 3 to 15. It is the standard tool for assessing impaired consciousness.
ABCD²
The ABCD² score estimates the short-term risk of stroke after a transient ischaemic attack (TIA) from five factors — Age, Blood pressure, Clinical features, Duration of symptoms, and Diabetes — for a total of 0 to 7, used to triage how urgently a TIA is assessed.
Acid–base & electrolytes
Corrected Calcium
Corrected (albumin-adjusted) calcium estimates what the total serum calcium would be if albumin were normal, because low albumin lowers measured total calcium. The Payne formula adds 0.8 mg/dL for every 1 g/dL the albumin is below 4.0 g/dL.
Serum Osmolality
Calculated serum osmolality estimates plasma osmolality from sodium, glucose and urea (BUN). In US units it is 2 × sodium + glucose ÷ 18 + BUN ÷ 2.8. Comparing it to a measured value gives the osmolal gap, which can flag toxic alcohols.
Corrected Sodium
Hyperglycaemia dilutes serum sodium, so the measured value underestimates the true sodium. The correction adds a factor times the glucose excess over 100 mg/dL: the classic Katz factor is 1.6 and the Hillier factor is 2.4 mmol/L per 100 mg/dL of glucose above normal.
Free Water Deficit
The free water deficit estimates the litres of water needed to correct hypernatraemia: deficit = total body water × (serum sodium ÷ 140 − 1), where total body water is body weight multiplied by a sex- and age-specific fraction. It is a guide to the replacement requirement, not a rate of correction.
Winter's Formula
Winter's formula gives the expected PaCO₂ in a simple metabolic acidosis — 1.5 × bicarbonate + 8 ± 2 mmHg — so you can check whether respiratory compensation is appropriate or a second acid–base disorder is present.
Critical care & emergency
NEWS2
NEWS2 is the UK Royal College of Physicians’ National Early Warning Score 2 — a standardised aggregate score of six bedside observations (respiratory rate, oxygen saturation, supplemental oxygen, blood pressure, pulse, consciousness and temperature) used to flag and track acute clinical deterioration in adults.
SOFA
The SOFA (Sequential Organ Failure Assessment) score grades dysfunction in six organ systems — respiratory, coagulation, liver, cardiovascular, central nervous system and renal — each from 0 to 4, for a total of 0 to 24, to describe the severity of critical illness and sepsis.
PERC
The PERC rule (Pulmonary Embolism Rule-out Criteria) is an eight-item decision rule used in emergency patients already judged to be at low risk of pulmonary embolism: if all eight criteria are absent, PE can be excluded without D-dimer or imaging. Any positive criterion makes the rule positive.
Ranson
Ranson’s criteria estimate the severity and mortality of acute (non-gallstone) pancreatitis from eleven parameters — five measured at admission and six over the next 48 hours. Each positive criterion scores one point; three or more indicate severe pancreatitis.
Parkland
The Parkland (Baxter) formula estimates the crystalloid (Lactated Ringer’s) volume for the first 24 hours of burn resuscitation: 4 mL × body weight in kg × percentage of total body surface area burned. Half is given in the first 8 hours from the time of the burn and half over the next 16 hours.
MEWS
The Modified Early Warning Score (MEWS) aggregates systolic blood pressure, heart rate, respiratory rate, temperature and conscious level into a single bedside score to flag deteriorating patients.
SIRS Criteria
The Systemic Inflammatory Response Syndrome (SIRS) criteria count four findings (temperature, heart rate, respiratory rate/PaCO₂, white-cell count); two or more define SIRS and, with infection, historically defined sepsis.
Gastroenterology & surgery
Alvarado
The Alvarado score (mnemonic MANTRELS) estimates the likelihood of acute appendicitis from eight clinical and laboratory findings — migratory right-lower-quadrant pain, anorexia, nausea/vomiting, RLQ tenderness, rebound tenderness, fever, leukocytosis and a left shift — for a total of 0 to 10.
Glasgow-Blatchford
The Glasgow-Blatchford Bleeding Score (GBS) is an admission risk score for acute upper-gastrointestinal bleeding, using blood urea, haemoglobin, systolic blood pressure, pulse, presentation with melaena or syncope, and hepatic or cardiac disease — needing no endoscopy. A score of 0 marks very-low-risk patients.
Rockall
The full Rockall score estimates the risk of rebleeding and death after acute upper-gastrointestinal bleeding from five factors — age, shock, comorbidity, the endoscopic diagnosis and stigmata of recent haemorrhage — for a total of 0 to 11. The pre-endoscopy (clinical) Rockall uses only the first three (0 to 7).
Glasgow-Imrie
The Glasgow-Imrie score (mnemonic PANCREAS) grades the severity of acute pancreatitis from eight criteria assessed within 48 hours — PaO₂, age, neutrophil/white-cell count, calcium, renal urea, LDH/AST, albumin and glucose — each scoring one point. A score of 3 or more predicts severe acute pancreatitis.
Infectious disease & ENT
Centor / McIsaac
The Centor score, with McIsaac’s age modification, estimates the probability of group A streptococcal pharyngitis from four clinical criteria — tonsillar exudate, tender anterior cervical nodes, fever by history, and absence of cough — plus an age adjustment, to guide rapid-strep testing and antibiotics.
FeverPAIN
FeverPAIN scores five features of a sore throat (Fever, Purulence, Attend rapidly, Inflamed tonsils, No cough/coryza) from 0 to 5 to estimate the chance of streptococcus and guide antibiotic decisions.
Haematology
Mentzer Index
The Mentzer index divides the mean corpuscular volume (MCV, fL) by the red-cell count (RBC, ×10¹²/L) to help distinguish beta-thalassaemia trait from iron-deficiency anaemia in a microcytic picture. A value under 13 suggests thalassaemia trait, and over 13 suggests iron deficiency.
ANC
The absolute neutrophil count (ANC) is the number of neutrophils per microlitre of blood: ANC = white-cell count × (percent segmented neutrophils + percent band neutrophils) ÷ 100. It is used to grade neutropenia, with an ANC under 500 /µL defining severe neutropenia and a high infection risk.
Mental health & screening
PHQ-9
The PHQ-9 is a nine-item depression questionnaire scored from 0 to 27. Each item is rated 0 (not at all) to 3 (nearly every day) over the last two weeks. Totals of 5, 10, 15 and 20 mark the thresholds for mild, moderate, moderately severe and severe depression.
GAD-7
The GAD-7 is a seven-item generalised-anxiety questionnaire scored from 0 to 21. Each item is rated 0 (not at all) to 3 (nearly every day) over the last two weeks. Totals of 5, 10 and 15 mark the thresholds for mild, moderate and severe anxiety, with 10 or more a common referral cut-point.
AUDIT-C
The AUDIT-C is a three-item alcohol-use screen scored from 0 to 12, taken from the first three questions of the AUDIT. It asks about frequency of drinking, typical quantity, and frequency of heavy episodes. A score of 4 or more in men and 3 or more in women suggests hazardous drinking.
CAGE Questionnaire
The CAGE questionnaire is a four-item alcohol screen asking about Cutting down, being Annoyed by criticism, feeling Guilty, and needing an Eye-opener; two or more "yes" answers is a positive screen.
Respiratory & sleep
STOP-BANG
The STOP-BANG questionnaire screens for obstructive sleep apnoea using eight yes/no items (Snoring, Tiredness, Observed apnoea, blood Pressure, BMI, Age, Neck circumference, Gender); higher scores indicate higher risk.
Epworth Sleepiness Scale
The Epworth Sleepiness Scale (ESS) measures average daytime sleepiness by rating the chance of dozing in eight everyday situations from 0 to 3, for a total of 0 to 24.
Medical disclaimer: These tools provide general health information only and are not a substitute for professional medical advice, diagnosis or treatment. Always consult a qualified doctor about your individual health. Editorial review: each calculator implements a published formula or clinical decision rule as published (the clinical scores cite their original publication on the tool page); nothing is invented. Last reviewed: 2 July 2026.