Reference

Calculators

41 free calculators that work on the page, each with its formula, normal range and how to read the result.

Reviewed by Alex G, BSN, RN, CEN, CCRN, CMC, NREMT-P · From the Reference tab of the app

Hemodynamics

• Cardiac Index (CI)Cardiac output scaled to body size, so flow can be compared between a small and a large patient.
• Cardiac Output (Fick Principle)Cardiac output from oxygen consumption and the arterial-to-mixed-venous oxygen content difference (the Fick principle).
• Cerebral Perfusion Pressure (CPP)MAP minus ICP, the pressure that drives blood through the brain; the number to protect after traumatic brain injury.
• Mean Arterial Pressure (MAP)Average pressure driving blood through the organs, worked from systolic and diastolic; the usual perfusion target in shock.
• Oxygen Delivery (DO₂)Oxygen carried to the tissues each minute, cardiac output times arterial oxygen content; falls with low output, anemia or hypoxemia.
• Pulmonary Vascular Resistance (PVR)Resistance the right ventricle pumps against in the lungs; raised in pulmonary hypertension, PE and hypoxic vasoconstriction.
• QTc (Bazett)Heart-rate-corrected QT for judging torsades risk with QT-prolonging drugs and low potassium or magnesium; Bazett over-corrects at fast rates.
• Shock IndexHeart rate over systolic pressure; a rising value can flag shock before blood pressure falls.
• Stroke Volume (SV)Blood ejected per beat, worked back from cardiac output and heart rate; shows whether low output is a pump problem or a rate problem.
• Systemic Vascular Resistance (SVR)Afterload of the left ventricle from MAP, CVP and cardiac output; low in vasodilatory shock, high in cardiogenic and hypovolemic shock.

Respiratory

• A-a GradientAlveolar minus arterial oxygen; separates hypoxemia from hypoventilation (normal gradient) from a lung problem (wide gradient).
• Alveolar Gas Equation (PAO₂)Expected alveolar oxygen pressure from FiO2, barometric pressure and PaCO2; the first step toward the A-a gradient.
• Arterial Oxygen Content (CaO₂)Oxygen carried in each dL of arterial blood from hemoglobin, saturation and dissolved O2; shows whether anemia or hypoxemia limits delivery.
• Minute VentilationRespiratory rate times tidal volume: the air moved per minute, which sets how fast CO2 is cleared.
• P/F Ratio (PaO₂/FiO₂)PaO₂ divided by FiO₂, the oxygenation measure that grades ARDS and triggers proning.
• Predicted Body Weight (PBW)Weight predicted from height and sex, the basis for lung-protective tidal volumes (6 mL/kg PBW in ARDS).
• SpO₂/FiO₂ RatioSpO₂ divided by FiO₂, a stand-in for the P/F ratio when there is no blood gas; valid only with SpO₂ 97% or less.
• Ventilator Rate for a Target PaCO₂The rate that should reach a target PaCO₂ if tidal volume, dead space and CO₂ production stay the same.

Renal & Electrolytes

• Anion GapSodium minus chloride and bicarbonate: sorts a metabolic acidosis into high-gap (lactate, ketones, toxins, renal failure) or normal-gap.

Acid-Base

• Winters' FormulaExpected PaCO₂ for a metabolic acidosis (Winter’s formula); a PaCO₂ outside the range means a second, respiratory disorder.

Fluids & Resuscitation

• Parkland FormulaCrystalloid for the first 24 hours after a major burn, from weight and burned surface area: half in the first 8 hours from the time of injury.

Clinical Scores

• APGAR ScoreNewborn assessment at 1 and 5 minutes after birth.
• Glasgow Coma Scale (GCS)Eye, verbal and motor responses scored 3 to 15; 8 or less usually means the airway needs protecting.
• Revised Trauma ScorePhysiologic triage score from GCS, systolic blood pressure and respiratory rate.

Drug Calculations

• Desired Over HaveVolume to give from the ordered dose and the dose on hand; the basic dose-to-volume check.
• Drip Rate (drops/min)Gravity-drip flow in drops per minute from volume, time and the tubing drop factor.
• mcg/kg/min to mL/hrConverts an ordered mcg/kg/min dose into the pump rate in mL/hr for a patient weight and bag concentration.
• Push-Dose EpinephrineVolume of a 10 mcg/mL push-dose epinephrine syringe for a given dose.
• Weight-Based Dose (mg/kg)Turns an ordered mg/kg dose into the total dose, and into mL when you know the concentration.

Pediatrics

• Pediatric Resuscitation DosesWeight-based emergency doses, energy and fluid for a child.
• Pediatric Vital Sign RangesNormal heart rate, respiratory rate and systolic blood pressure by age.
• Pediatric Weight EstimateEstimates a child’s weight from age when no scale or length-based tape is available.

IV Therapy

• mcg/min to mL/hrPump rate for infusions ordered in mcg/min, such as nitroglycerin.

Conversions

• Length: Inches and CentimetersConverts between inches and centimeters.
• Temperature: °F and °CConverts between Fahrenheit and Celsius.
• Weight: Pounds and KilogramsConverts between pounds and kilograms.

Airway & Oxygen

• Oxygen Cylinder DurationHow long a cylinder will last at a given flow.
• Pediatric ET Tube Size and DepthEstimates endotracheal tube size and insertion depth from age.

Trauma & Burns

• Burn Fluids (ABA Consensus 2 mL/kg)Initial fluid rate for major burns using the American Burn Association consensus formula.
• Burn Size (Rule of Nines)Total body surface area burned from the regions involved.

Neuro Scores

• NIH Stroke Scale (NIHSS)The standard 15-item stroke examination: scores neurological deficit from 0 to 42.

For education and exam preparation only. Follow your institution’s protocols. For education and exam preparation only. Not a substitute for clinical judgment, your local protocols or medical direction. Not affiliated with or endorsed by any certifying body (full notice in Settings).