Our Methodology: The Gault Standard
How we build, cite, and clinician-review every calculator.
The Gault Standard is the set of rules behind every calculator here. Every calculation follows the validated Cockcroft-Gault lineage, every clinical value is cited to a primary source, and every clinical page is reviewed by a credentialed clinician before it is marked production-ready.
The Historical Anchor
Donald Cockcroft and Henry Gault published the creatinine clearance equation in the journal Nephron in 1976, deriving it from a cohort of hospitalised patients and validating the estimate against measured clearance. Our calculators trace back to that paper. Dr. Henry Gault (1925-2003) was a Canadian nephrologist and is the historical namesake and methodology anchor for this site. He is not a current medical reviewer, and no content here is attributed to him as a reviewer. Modern eGFR work has moved on to the race-free CKD-EPI 2021 equation and KDIGO guidance, both of which we follow for staging.
How We Verify Clinical Values
- Formula coefficients are checked against the original publications and the National Kidney Foundation.
- Normal ranges and CKD cutoffs follow KDIGO and NKF; ranges that vary by laboratory are noted as such.
- Drug thresholds are checked against the FDA label and standard renal-dosing references, then cited.
- The Cockcroft-Gault dosing-weight rule follows Winter and colleagues (2012) and the FDA 2024 guidance on pharmacokinetics in renal impairment, with ideal body weight from the Devine formula.
- The calculator engine is unit-tested against published worked examples before any tool ships.
The Calculator Engine Is Tested
Each formula lives in a pure, typed module with its own unit tests. Before a calculator goes live, those tests confirm it reproduces the worked examples published by reference sources for the same inputs. A Cockcroft-Gault result here therefore matches a Cockcroft-Gault result computed by hand or by an established reference tool. Unit conversions, body-weight rules, and edge cases are tested the same way. A formula stays flagged for clinician review even when its tests pass; passing tests prove the arithmetic, not the clinical appropriateness.
How We Choose the Dosing Weight
The Cockcroft-Gault equation multiplies by body weight, so the calculators apply one documented rule. It is based on actual weight compared with ideal body weight (IBW) from the Devine formula (men 50 kg, women 45.5 kg, plus 2.3 kg per inch over 5 feet):
- Actual weight below IBW: actual body weight.
- Actual weight from IBW up to 130% of IBW: ideal body weight.
- Actual weight more than 130% of IBW: adjusted body weight, IBW + 0.4 × (actual − IBW).
The rule rests on Winter and colleagues (2012). They found actual weight unbiased in underweight patients and IBW unbiased in patients of normal weight. Adjusted body weight with a 0.4 factor was the least biased and most accurate option in overweight, obese, and morbidly obese patients. The FDA 2024 guidance on pharmacokinetics in renal impairment supports the same direction. In overweight or obese people, IBW or adjusted body weight is likely to give a more accurate Cockcroft-Gault estimate than actual body weight. The rule is not universal: some hospitals use 120% of IBW instead of 130%, and trial protocols and drug labels can set their own rule, which then takes priority. SWOG Policy 38, which caps the weight at 140% of IBW, is the example we cite.
Clinician Review and Refresh
Fact-checking and citation raise trust, but they do not replace human sign-off. A credentialed clinician reviews each page and signs off on its clinical values, and each page shows the date it was last reviewed. After publication, every clinical page is re-checked on a three-to-six-month cycle so that changing guidelines, updated drug labels, and new evidence are reflected rather than left to drift. See our medical reviewers.
Why We Cite Primary Sources
We cite primary sources because, on a medical site, a number carries no weight without a source. We attach a real citation to every clinical value (a formula coefficient, a normal range, a drug threshold). We prefer the primary publication or a recognised body such as the National Kidney Foundation, KDIGO, or an FDA label over a secondary summary. When two reputable sources disagree, we follow the more authoritative one, note the discrepancy, and cite both. A reader, or a clinician checking our work, can then trace any claim back to where it came from rather than taking it on trust.
About the Images
The photos on this site are AI-generated illustrations made for this site. They show generic clinical settings and objects, not real patients, staff, or our medical reviewer. They are not medical images and are not used to make any clinical point.