Free Pediatric GFR Calculator

Pediatric GFR Estimation for Children

This free online Pediatric GFR Calculator (also called a Child GFR Calculator) provides a pediatric kidney function test by estimating glomerular filtration rate in individuals up to 18 years old. Because children's kidney function assessment requires different formulas than adults, this tool specifically uses validated pediatric equations. Note that while this calculator offers helpful screening data, it cannot replace a professional medical diagnosis.

Understanding Pediatric Glomerular Filtration Rate

Glomerular filtration rate (GFR) reflects how efficiently the kidneys filter waste from the blood. It is expressed in mL/min per 1.73 m² of body surface area—a normalization that accounts for size differences in growing children. Because body surface area changes with age, pediatric formulas use the child’s height as a key adjustment factor. For a kidney function test in children, GFR is the essential indicator for detecting early renal impairment.

Three Established Pediatric GFR Equations

The National Kidney Foundation endorses three primary methods for estimating GFR in children. This Pediatric eGFR Calculator computes all three, allowing cross‑comparison of results.

1. Bedside Schwartz Equation (Creatinine‑Based)

The Bedside Schwartz Equation GFR (updated in 2009) is the standard method for children aged 1–18. It avoids the overestimation problems of older versions.

$$\mathrm{GFR} = 41.3 \times \frac{\mathrm{height}}{\mathrm{SCr}}$$

where:

• $\mathrm{height}$ is measured in meters;
• $\mathrm{SCr}$ is standardized serum creatinine in mg/dL.

This equation relies on only two routine inputs, making it convenient for clinical settings.

2. Cystatin C‑Based Equation (2012)

When creatinine levels are unstable, cystatin C offers an alternative marker. The formula is:

$$\mathrm{eGFR} = 70.69 \times \mathrm{Scys}^{-0.931}$$

where $\mathrm{Scys}$ is standardized serum cystatin C in mg/L. This test serves as an excellent confirmatory tool, especially when creatinine fluctuates.

3. Combined Creatinine‑Cystatin C (CKiD) Equation (2012)

The CKiD GFR Equation uses both creatinine and cystatin C, plus blood urea nitrogen (BUN) and sex, for enhanced accuracy:

$$\mathrm{GFR} = 39.8 \times \left(\frac{\mathrm{height}}{\mathrm{SCr}}\right)^{0.456} \times \left(\frac{1.8}{\mathrm{Scys}}\right)^{0.418} \times \left(\frac{30}{\mathrm{BUN}}\right)^{0.079} \times a \times \left(\frac{\mathrm{height}}{1.4}\right)^{0.179}$$

where:

• $\mathrm{height}$ is in meters;
• $\mathrm{SCr}$ is standardized serum creatinine in mg/dL;
• $\mathrm{Scys}$ is standardized serum cystatin C in mg/L;
• $\mathrm{BUN}$ is blood urea nitrogen in mg/dL;
• $a = 1$ for females and $1.076$ for males.

This comprehensive equation is recommended when single‑marker results are uncertain.

Interpreting GFR Results in Children

The table below outlines the typical classification of kidney function stages based on estimated GFR. All values are expressed in mL/min/1.73 m².

eGFR (mL/min/1.73 m²)	Kidney Function Stage
≥ 90	Normal or minimal damage with normal function
60–89	Mild loss of kidney function
45–59	Mild to moderate loss
30–44	Moderate to severe loss
15–29	Severe loss
< 15	Kidney failure

A single low result does not automatically indicate disease; trends over time and a full clinical picture are essential for diagnosis.