What is the updated Schwartz formula?

The 2009 bedside Schwartz equation estimates GFR in children as 0.413 multiplied by height in centimetres divided by serum creatinine in mg/dL. The single constant of 0.413 replaced the older age and sex specific constants once enzymatic, standardised creatinine assays became common.

Why is the constant 0.413 for everyone?

The original Schwartz constants were derived for an older, less specific creatinine assay. When creatinine is measured by an IDMS-traceable enzymatic method, a single constant of 0.413 fits children aged 1 to 17 across both sexes, which simplified the bedside formula considerably.

Can I enter creatinine in micromol/L?

Yes. Select micromol/L and the tool divides by 88.4 to convert to mg/dL before applying the formula, since the Schwartz constant is defined for mg/dL. The converted value is shown so you can check it.

Is this valid during acute kidney injury?

No. Like all creatinine-based estimates, Schwartz assumes a steady state. During rapidly changing function such as acute kidney injury the creatinine lags behind true GFR, so the estimate can be misleading. It is validated for chronic kidney disease.

Does it work for neonates?

Not reliably. The bedside Schwartz formula is validated for children aged roughly one year and older. Neonates and young infants have different creatinine handling and require neonatal-specific approaches.

Paediatric GFR Estimator (Schwartz Formula)

The Schwartz formula is the standard bedside estimate of kidney function in children. Because children vary so widely in size, it scales glomerular filtration rate directly with height rather than relying on adult equations that assume a fixed body habitus.

How it works

The updated 2009 bedside equation is deliberately simple:

eGFR = 0.413 x height(cm) / serum creatinine(mg/dL)

The constant of 0.413 applies to all children aged 1 to 17 when creatinine is measured by a modern IDMS-traceable enzymatic assay. If your laboratory reports creatinine in micromol per litre, divide by 88.4 to convert to mg/dL first; the tool does this automatically and shows the converted value.

Interpretation and notes

The result is expressed per 1.73 square metres of body surface area, the standard normalisation, and is paired with a chronic kidney disease stage as a guide. The estimate assumes a steady state, so it is unreliable during acute kidney injury when creatinine lags behind true function, and it can be skewed by unusually high or low muscle mass. It is validated for chronic kidney disease in children from about one year of age and is not intended for neonates.