Schwartz GFR Calculator

Schwartz GFR Calculator for Pediatrics. Read the result against pediatric CKD stages (all mL/min/1.73 m2): G1 at or above 90 with a marker of kidney damage, G2 60 to 89, G3a 45 to 59, G3b 30 to 44, G4 15 to 29, and G5 below 15. Because the constant 0.413 was derived in a cohort with a median measured GFR near 41, the bedside equation performs best in the impaired range and tends to lose accuracy above roughly 75 to 90, where it can overestimate true GFR. Trend matters more than any single value: a falling ratio over serial visits signals progression even while the absolute number still looks reassuring.

How this calculator works

The bedside Schwartz equation estimates GFR in children and adolescents as eGFR (mL/min/1.73 m2) = k x height (cm) / serum creatinine (mg/dL). The 2009 CKiD revision fixed k at 0.413 for all children when creatinine is measured by an IDMS-traceable enzymatic method, replacing the older age- and sex-specific constants (0.33, 0.45, 0.55, 0.70) that were calibrated to the higher readings of the Jaffe assay. It normalizes to body surface area, so no separate BSA adjustment is needed, and it collapses the two variables that dominate pediatric muscle mass and creatinine generation (linear growth and filtration) into a single ratio.

When to use this calculator

Use for children roughly 1 to 18 years old with a standardized (enzymatic, IDMS-traceable) serum creatinine and an accurately measured recumbent length or standing height. It is the workhorse for staging pediatric CKD, tracking trajectory across clinic visits, and adjusting renally cleared drug doses. Do not apply it to neonates or infants under 1 year (creatinine still reflects maternal contribution and the constant is unvalidated), to adults, or when the older Jaffe-calibrated constant of 0.55 is being paired with a modern enzymatic creatinine, which systematically overestimates GFR.

Inputs used

  • Height
  • Serum creatinine
  • Equation coefficient

Clinical interpretation

Read the result against pediatric CKD stages (all mL/min/1.73 m2): G1 at or above 90 with a marker of kidney damage, G2 60 to 89, G3a 45 to 59, G3b 30 to 44, G4 15 to 29, and G5 below 15. Because the constant 0.413 was derived in a cohort with a median measured GFR near 41, the bedside equation performs best in the impaired range and tends to lose accuracy above roughly 75 to 90, where it can overestimate true GFR. Trend matters more than any single value: a falling ratio over serial visits signals progression even while the absolute number still looks reassuring.

Worked example

A 10-year-old with height 140 cm and enzymatic serum creatinine 0.6 mg/dL: eGFR = 0.413 x 140 / 0.6 = 96.4 mL/min/1.73 m2, which is normal renal function (CKD stage G1). If that same child's creatinine rose to 1.8 mg/dL at the same height, eGFR = 0.413 x 140 / 1.8 = 32.1 mL/min/1.73 m2, placing them in CKD stage G3b and prompting nephrology referral, medication dose review, and closer monitoring.

Limitations and safety notes

The estimate is only as good as its inputs and fails when creatinine generation departs from typical muscle mass, for example in severe malnutrition, muscle-wasting or neuromuscular disease, amputees, or after high-protein or creatine intake. It assumes a standardized enzymatic creatinine; using it with a Jaffe-based value or the wrong constant introduces systematic bias. It was validated in children 1 to 16 with CKD and is unreliable at near-normal GFR and in infants under 1 year. It ignores acute non-steady-state changes, so during rapidly evolving AKI the equation lags true GFR; when precision is critical, a cystatin C-based estimate (CKiD combined equation) or measured iohexol clearance is preferable.

Frequently asked questions

Why 0.413 instead of the old 0.55?

The 1976 constants were calibrated to Jaffe-method creatinine, which reads higher than modern enzymatic IDMS-traceable assays. When labs switched methods, the old constants overestimated GFR. The 2009 CKiD study re-derived a single constant of 0.413 against iohexol clearance for standardized enzymatic creatinine.

Do I need height in cm or meters?

The bedside equation uses height in centimeters with the constant 0.413. The full CKiD research equation uses height in meters. Mixing units is a common error; confirm your formula's expected input before entering values.

Can I use this in a newborn?

No. Below roughly 1 year of age serum creatinine still partly reflects maternal levels and muscle mass is low, so the constant is not validated. Neonatal GFR estimation requires age-specific approaches.

Is a single normal eGFR reassuring?

Not by itself. The bedside equation is least accurate at higher GFR and can overestimate, so a value near or above 90 does not exclude early kidney damage. Interpret alongside proteinuria, imaging, and the trend across visits.

When should I use cystatin C instead?

When muscle mass is atypical (wasting, neuromuscular disease, amputation) or when a more precise estimate is needed, the CKiD cystatin C or combined creatinine-cystatin C equation reduces muscle-related bias; measured clearance remains the reference standard.

References

  • Schwartz GJ, Muñoz A, Schneider MF, Mak RH, Kaskel F, Warady BA, Furth SL. New equations to estimate GFR in children with CKD. J Am Soc Nephrol. 2009. PMID: 19158356.
  • Schwartz GJ, Haycock GB, Edelmann CM, Spitzer A. A simple estimate of glomerular filtration rate in children derived from body length and plasma creatinine. Pediatrics. 1976. PMID: 951142.
  • Staples A, LeBlond R, Watkins S, Wong C, Brandt J. Validation of the revised Schwartz estimating equation in a predominantly non-CKD population. Pediatr Nephrol. 2010. PMID: 20652327.

Editorial review and citation methodology

Reviewed by the Quick Medical Calculator Editorial Team. Last reviewed: June 12, 2026. The review checks calculator inputs, intended population, interpretation, limitations, and source alignment.

  • Prefer original validation studies for scoring systems and prediction tools.
  • Use current specialty society guidance, transplant allocation policy, public health guidance, or regulator resources when they govern clinical use.
  • Include limitations and safety notes when a calculator is population-specific, context-dependent, or unsuitable as a standalone decision tool.

Related reviewed calculators