Schwartz Equation (Pediatric eGFR) Explained
Estimating GFR in children from height and creatinine.
Medically reviewed by Dr. Rishi Kumar Kafle, MBBS, MD, FASN · Last reviewed June 2026
The bedside Schwartz equation estimates eGFR in children as 0.413 × height in cm ÷ serum creatinine in mg/dL, in mL/min/1.73m². Because children's muscle mass and creatinine differ from adults', the adult equations do not apply.
Every Term Defined
The bedside form is deliberately simple — a single constant, the child's height, and serum creatinine. The height term is what makes it work in children: as a child grows, both muscle mass and kidney size scale with height, so height stands in for body size where weight and age cannot.
| Term | Value | Role |
|---|---|---|
| Constant (k) | 0.413 | IDMS-traceable bedside constant |
| Height | cm | proxy for muscle mass and body size in growing children |
| Serum creatinine | mg/dL | the filtration marker in the denominator |
The 0.413 constant is the updated, IDMS-traceable value from the 2009 CKiD study; older texts used 0.55, which applied to non-standardised creatinine assays. Use the standardised value with modern lab results, and convert with the creatinine unit converter if your lab reports µmol/L.
A Worked Example
For a child who is 120 cm tall with a serum creatinine of 0.5 mg/dL, the estimate is 0.413 × 120 ÷ 0.5 = 99 mL/min/1.73m² — normal pediatric kidney function. A taller child or a lower creatinine raises the estimate; a rising creatinine lowers it.
When to Use It
Use Schwartz for patients under 18. It is the standard bedside method for pediatric eGFR and is preferred over adult equations, which assume adult body composition. For adults, use the CKD-EPI 2021 eGFR calculator or Cockcroft–Gault creatinine clearance for dosing. See creatinine clearance in pediatrics.
Why Children Need Their Own Equation
Adult eGFR equations such as CKD-EPI 2021 and MDRD assume adult body composition and use age as a proxy for declining muscle mass. In children, muscle mass is still building and rises with growth rather than falling with age, so an age term would point the wrong way. Height captures this directly: a taller child has more muscle, produces more creatinine, and has larger kidneys, so for a given serum creatinine a taller child has greater filtration. That is why the bedside Schwartz equation puts height in the numerator and is the standard pediatric tool.
History of the Constant
The original Schwartz equation dates from 1976 and used a constant of 0.55 with the creatinine assays of the time. When laboratories standardised creatinine measurement to isotope-dilution mass spectrometry, the 2009 CKiD study re-derived the bedside constant as 0.413. Using the old 0.55 with a modern standardised creatinine would overestimate eGFR, so it is important to pair the 0.413 constant with today's lab values. This site uses the IDMS-traceable 0.413 form.
How to Read the Result
Pediatric GFR matures over the first two years of life and then sits in the adult-normal range, so for most children beyond infancy a result near or above 90 mL/min/1.73m² is normal. Lower values are interpreted against pediatric CKD categories much as in adults, but staging in children is a specialist judgement that also weighs growth, the underlying cause, and trend over time rather than a single number. A falling Schwartz estimate over serial visits is more informative than one isolated value.
Strengths and Limitations
Its strength is that it needs only height and creatinine, both routinely available, and it was validated in children with chronic kidney disease. Its limitations are shared with all creatinine equations: it assumes average muscle mass and a steady state, so it is less reliable in malnutrition, unusual body habitus, or rapidly changing function. Accurate height measurement matters, since the estimate scales directly with it — a small error in height moves the eGFR proportionally. See creatinine clearance in pediatrics for the wider clinical context.
The Transition to Adult Equations
There is no single moment at which a child's kidneys become an adult's, so the handover from Schwartz to CKD-EPI 2021 is a clinical judgement made around the late teens, once growth is essentially complete and adult body composition is established. Some pediatric nephrology services continue Schwartz to age 18 for consistency in tracking a known patient, then re-baseline on an adult equation. What should not happen is applying an adult equation to a young child or the bedside Schwartz constant to a fully grown adult — each is calibrated for its own population, and crossing them introduces avoidable error.