Acid-Base Calculator

Category: Other Health
- March 30, 2025
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Calculate acid-base status and diagnose disorders based on arterial blood gas (ABG) values. This calculator helps interpret pH, PaCO2, HCO3-, and other values to identify metabolic and respiratory disorders.

Enter Patient Values

units
mmHg
mEq/L
mEq/L
mEq/L
mEq/L
g/dL
mmHg
%

Optional Parameters

mmol/L
mg/dL
mg/dL

Patient Demographics

years
°C

Advanced Options

About Acid-Base Disorders

Acid-base disorders are disturbances in the hydrogen ion (H+) concentration that can be potentially serious if not recognized and treated properly. The body maintains a normal pH through respiratory and metabolic mechanisms.

Primary Acid-Base Disorders
  • Respiratory Acidosis: pH < 7.35, PaCO₂ > 45 mmHg
  • Respiratory Alkalosis: pH > 7.45, PaCO₂ < 35 mmHg
  • Metabolic Acidosis: pH < 7.35, HCO₃⁻ < 22 mEq/L
  • Metabolic Alkalosis: pH > 7.45, HCO₃⁻ > 26 mEq/L
Compensation Mechanisms

The body attempts to normalize pH through compensatory mechanisms:

  • Respiratory Compensation: Changes in ventilation to adjust PaCO₂
  • Metabolic Compensation: Renal adjustments to bicarbonate levels
Anion Gap

The anion gap helps differentiate causes of metabolic acidosis:

  • Normal (8-12 mEq/L): Non-anion gap metabolic acidosis (NAGMA)
  • Elevated (>12 mEq/L): Anion gap metabolic acidosis (AGMA)
Delta Ratio

The delta ratio helps identify mixed metabolic disorders:

  • Delta Ratio < 0.8: AGMA with concurrent NAGMA
  • Delta Ratio 0.8-1.2: Simple AGMA
  • Delta Ratio > 1.2: AGMA with concurrent metabolic alkalosis
Common Causes of Acid-Base Disorders
  • Respiratory Acidosis: Hypoventilation, COPD, sedatives
  • Respiratory Alkalosis: Hyperventilation, anxiety, sepsis
  • Metabolic Acidosis (AGMA): Ketoacidosis, lactic acidosis, renal failure, toxins
  • Metabolic Acidosis (NAGMA): Diarrhea, RTA, ureterosigmoidostomy
  • Metabolic Alkalosis: Vomiting, diuretics, hypokalemia

Anion Gap: Na⁺ - (Cl⁻ + HCO₃⁻)

Corrected HCO₃⁻: HCO₃⁻ + 2.5 × (4 - Albumin)

Delta Ratio: (Anion Gap - 12) / (24 - HCO₃⁻)

Winter’s Formula (for Metabolic Acidosis): 1.5 × HCO₃⁻ + 8 ± 2

P/F Ratio: PaO₂ / (FiO₂ / 100)

A–a Gradient: ((FiO₂ × (Patm − PH₂O)) − (PaCO₂ / 0.8)) − PaO₂

What Is the Acid-Base Calculator?

The Acid-Base Calculator is a medical tool that helps assess a patient’s acid-base balance by analyzing key blood gas values. It supports clinical decision-making by identifying respiratory and metabolic disturbances in blood pH, carbon dioxide (PaCO₂), and bicarbonate (HCO₃⁻) levels.

Important: This is not a pH Calculator. A typical pH Calculator is used in chemistry to find the acidity or alkalinity of solutions in controlled reactions. This tool, instead, evaluates human physiological data to assist in medical assessments based on arterial blood gas (ABG) results.

Why Use This Calculator?

Accurate interpretation of ABG values is crucial in emergency medicine, intensive care, and other clinical settings. The calculator provides fast insights that can guide treatments, such as ventilator adjustments or metabolic support.

Using this tool, you can:

  • Identify primary acid-base disorders like respiratory acidosis or metabolic alkalosis
  • Check if the body is compensating for an imbalance
  • Calculate values like anion gap and delta ratio for deeper analysis
  • Evaluate oxygenation using the P/F ratio and A–a gradient
  • Get automated interpretation and clinical suggestions

How to Use the Calculator

Follow these steps to analyze a patient's acid-base status:

  1. Enter values such as pH, PaCO₂, and HCO₃⁻ in the "Enter Patient Values" section.
  2. Optionally, input additional values like sodium, potassium, chloride, albumin, and oxygenation data (PaO₂ and FiO₂).
  3. You can also add patient demographics such as age, gender, and temperature.
  4. Select the decimal precision and whether you want to view detailed calculations or simplified interpretation.
  5. Click "Analyze ABG" to see results instantly.
  6. To clear the form, click "Reset".

What the Results Show

After clicking Analyze, the calculator displays:

  • Primary Disorder: The main acid-base abnormality detected
  • Compensation: Whether the body is adjusting to restore balance
  • Detailed Calculations: Values like anion gap, delta ratio, P/F ratio, and A–a gradient
  • Interpretation: A plain-language summary of the findings
  • Clinical Recommendations: Suggestions based on the disorder type and results

Who Is This For?

This calculator is ideal for healthcare professionals, medical students, or anyone learning about ABG analysis. It's a practical tool for understanding respiratory and metabolic status quickly, much like how a GFR Calculator is used to estimate kidney function or how a TDEE Calculator helps in managing energy expenditure.

Common Use Cases

It can be especially helpful when evaluating:

  • Critically ill patients with altered breathing or consciousness
  • Post-operative patients in recovery rooms
  • Cases involving sepsis, diabetic ketoacidosis, or poisoning

FAQ

Is this the same as a chemistry pH or titration calculator?

No. This calculator is built for clinical blood gas interpretation, not chemical reactions in a lab setting.

Does it require all values to work?

No. You can use only the key fields (pH, PaCO₂, and HCO₃⁻), but adding more values gives you deeper insight.

Can I use this to diagnose patients?

This tool is an aid, not a substitute for medical judgment. Always interpret results in clinical context.

What does “compensated” mean in the results?

It means the body is attempting to correct the pH by adjusting breathing (respiratory) or kidney function (metabolic).

How is this different from tools like the BAC Calculator or Macro Calculator?

While a BAC Calculator estimates blood alcohol levels and a Macro Calculator tracks daily nutrition macros, this tool is focused on assessing medical parameters related to acid-base balance and blood gas interpretation.

Final Thoughts

Whether you're managing a patient in the ICU or studying for your next medical exam, this Acid-Base Calculator simplifies the process of interpreting complex ABG data. Like other calculators such as the Body Surface Area Calculator or Protein Calculator, it's a valuable tool that saves time and improves accuracy in clinical decision-making.