Winters Formula Calculator For Metabolic Acidosis

Establishes the level of PCO2 compensation in metabolic and mixed acidosis cases, based on bicarbonate.

Read more about the Winters’ formula and when to use it, in the text below the form.

Winters formula calculator uses the bicarbonate level (HCO3-) to determine the partial CO2 pressure (PCO2) compensation in patients with metabolic and mixed acidosis.

The formula was developed by Dr Winters specifically to predict the level of respiratory compensation that would be necessary to recover from acidosis.

The formula used by this metabolic acidosis compensation calculator is:

Expected PCO2 = 1.5 x HCO3- + 8 +/- 2

Which leads to the creation of a compensation interval between 1.5 x HCO3- + 6 and 1.5 x HCO3- + 10.

Bicarbonate (HCO3-)
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Steps on how to print your input & results:

1. Fill in the calculator/tool with your values and/or your answer choices and press Calculate.

2. Then you can click on the Print button to open a PDF in a separate window with the inputs and results. You can further save the PDF or print it.

Please note that once you have closed the PDF you need to click on the Calculate button before you try opening it again, otherwise the input and/or results may not appear in the pdf.


Winters formula explained

In cases of metabolic acidosis, medical professionals may be required to evaluate PCO2 compensation in connection with the level of bicarbonate [HCO3-].

The Winters formula calculator provides the lower and upper values of partial CO2 pressure in mmHg:

Expected pCO2 = 1.5 x HCO3- + 8 +/- 2

Which means that the creation of a compensation interval between 1.5 x HCO3- + 6 and 1.5 x HCO3- + 10.

The rule is that for every 1 mEq/L reduction of plasma bicarbonate, there is a 1.2 mmHg PCO2 reduction, but only to a minimum of 10 - 15 mmHg.

The clinician should compare the patient’s data with the computed value:

■ If the value retrieved from patient data is included in the computed interval, then respiratory compensation is adequate;

■ If the patient’s value is higher than interval, this is indicative of primary respiratory acidosis;

■ If the patient’s value is lower than interval, this is indicative of primary respiratory alkalosis.

To be exact, where respiratory alkalosis is suspected, Winters formula should be adapted to the following:

PCO2 = 0.7 x HCO3- + 20 +/- 5 mmHg meaning the interval between 0.7 x HCO3- + 15 and 0.7 x HCO3- + 25.


When is compensation required

The formula developed by Dr Winters is suitable for cases where the level of respiratory compensation needs to be adapted for the patient to recover from acidosis.

These results are used in the analysis of acid base disorders along with the anion gap.

In metabolic acidosis, the bicarbonate reduction may result even in extracellular imbalances and loss of bicarbonate in urine.

The body responds by attempting to restore the PCO2/HCO3- ratio which means a reduction of what is seen as excess PCO2.

The physiological mechanism is based on signals from the low arterial pH that stimulate chemoreceptors in charge with respiration.

Therefore, an increase in alveolar ventilation takes place, which sometimes leads to Kussmaul type respiration.


Original source

Asch MJ, Dell RB, Williams GS, Cohen M, Winters RW. Time course for development of respiratory compensation in metabolic acidosis. J Lab Clin Med. 1969; 73(4):610-5.


Albert MS, Dell RB, Winters RW. Quantitative displacement of acid-base equilibrium in metabolic acidosis. Ann Intern Med. 1967; 66(2):312-22.

Specialty: Endocrinology

System: Endocrine

Objective: Determination

Type: Calculator

No. Of Variables: 1

Year Of Study: 1969

Article By: Denise Nedea

Published On: May 24, 2017 · 03:04 PM

Last Checked: May 24, 2017

Next Review: May 24, 2023