Pediatric Glomerular Filtration Rate
Estimate pediatric kidney function with the Bedside Schwartz, Cystatin C-based, and CKiD equations. Free online eGFR calculator for children with stage classification.
About This Calculator
The Pediatric Glomerular Filtration Rate (GFR) Calculator estimates kidney function in children aged 1 to 18 years using the most current and validated formulas recommended by the National Kidney Foundation. Unlike adult GFR calculators that rely on age-adjusted equations, pediatric GFR estimation uses height-based formulas to account for the changing body surface area throughout childhood and adolescence.
The primary method is the Bedside Schwartz equation (2009): GFR = 41.3 × (height in meters ÷ serum creatinine in mg/dL). This updated formula uses a single constant of 41.3, replacing the older variable k-factor approach, and relies on standardized creatinine measurements to avoid overestimation. When cystatin C is available, the Cystatin C-based equation (eGFR = 70.69 × Scys⁻⁰·⁹³¹) provides a confirmatory estimate independent of muscle mass. For the most comprehensive assessment, the CKiD combined equation integrates height, creatinine, cystatin C, BUN, and sex for optimal accuracy.
GFR results are reported in mL/min/1.73m² (standardized body surface area) and classified into CKD stages: normal (≥90), mild loss (60-89), mild-to-moderate loss (45-59), moderate-to-severe loss (30-44), severe loss (15-29), and kidney failure (<15). Regular GFR monitoring is essential for children with chronic kidney disease, congenital anomalies of the kidney and urinary tract (CAKUT), glomerulonephritis, or those receiving nephrotoxic medications.
Regional Notes
India: Indian labs are increasingly adopting standardized creatinine assays (IDMS-traceable). The cost of a basic kidney function test (creatinine, BUN) is approximately ₹150-400. Cystatin C testing is available at major hospital labs for ₹600-1200. The Indian Society of Pediatric Nephrology recommends annual GFR screening for children with CAKUT, reflux nephropathy, or a family history of kidney disease.
US: The Kidney Disease: Improving Global Outcomes (KDIGO) guidelines recommend the Bedside Schwartz equation as the preferred method for children. Cystatin C testing is covered by most insurance plans when ordered for renal function assessment. NHANES data indicates approximately 1 in 5,000 US children has stage 3-5 CKD.
UK: The UK National Institute for Health and Care Excellence (NICE) recommends the Bedside Schwartz equation for pediatric GFR estimation and cystatin C as a confirmatory test when creatinine-based estimates may be unreliable (low muscle mass, liver cirrhosis, nutritional disorders). The NHS offers free kidney function testing for at-risk children.
Frequently Asked Questions
What is the pediatric GFR calculator?
The pediatric GFR calculator estimates glomerular filtration rate in children aged 1-18 years using the Bedside Schwartz equation (2009), Cystatin C-based equation (2012), and the combined CKiD equation (2012). It requires height and serum creatinine, with optional cystatin C and BUN for more comprehensive results.
How is pediatric GFR different from adult GFR?
Pediatric GFR uses height-based formulas instead of age-based because children's body surface area changes substantially during growth. The Bedside Schwartz equation (GFR = 41.3 × height/creatinine) is the standard for children, while adults use the CKD-EPI or MDRD equations that incorporate age, sex, and race.
What is a normal GFR for a child?
A normal GFR for children is 90 mL/min/1.73m² or above, which indicates healthy kidney function. Values between 60-89 suggest mild kidney damage with mild loss of function. Levels below 60 indicate moderate to severe kidney impairment that requires medical attention.
What creatinine level indicates kidney failure in children?
There is no single creatinine level that defines kidney failure. Creatinine must be interpreted with height and age. A GFR below 15 mL/min/1.73m² indicates kidney failure (Stage G5) regardless of the absolute creatinine value. The Bedside Schwartz equation converts creatinine and height into the meaningful GFR value.
What is the Bedside Schwartz formula?
The Bedside Schwartz formula is GFR = 41.3 × (height in meters / serum creatinine in mg/dL). Updated in 2009, it replaced the older Schwartz formula with a constant of 41.3 (instead of the variable k factor) and uses standardized creatinine measurements for more accurate results without overestimation.
Can this calculator be used for infants under 1 year?
This calculator is validated for children aged 1-18 years. For infants under 1 year, different formulas with varying k constants (0.33 for full-term infants, 0.45 for infants 1-2 years) may be more appropriate. Consult a pediatric nephrologist for accurate GFR assessment in neonates and infants.
What units does this calculator accept?
Height is accepted in centimeters, serum creatinine in mg/dL (standardized), cystatin C in mg/L, and BUN in mg/dL. If your lab reports creatinine in μmol/L, divide by 88.4 to convert to mg/dL. For BUN reported as mmol/L, multiply by 2.8 to convert to mg/dL.
Should I add cystatin C and BUN for a better estimate?
Adding cystatin C provides a confirmatory estimate independent of muscle mass, which is especially useful in children with reduced muscle mass or those on a vegetarian diet. Adding both cystatin C and BUN enables the combined CKiD equation, which gives the most comprehensive eGFR estimate but requires more lab values.