π§ͺ Pediatric GFR Calculator
Bedside Schwartz eGFR from height and creatinine.
For informational purposes only, not medical advice. Consult a healthcare professional.
Glomerular filtration rate is the headline number for kidney function, and in children it is estimated with the bedside Schwartz formula: 0.413 times height in centimeters divided by serum creatinine in mg/dL. The constant 0.413 was calibrated against measured GFR in children with chronic kidney disease, and the equation remains the standard bedside estimator in pediatrics. This calculator runs it and stages the result by the KDIGO chronic kidney disease categories, for education and clinical reference.
How to Use This Calculator
Enter the height in centimeters and the serum creatinine in mg/dL from a recent lab. The bedside Schwartz equation gives the estimated GFR.
Measure height accurately in centimeters. The formula scales directly with height, so a sloppy measurement becomes a sloppy eGFR.
Enter serum creatinine in mg/dL as reported by the lab. If your lab reports micromol/L, divide by 88.4 first.
Read the eGFR in mL/min/1.73 m2 plus the CKD stage band. Trends across serial labs matter more than any single value.
How the Math Works
Multiply 0.413 by height in cm, then divide by serum creatinine in mg/dL. A child 120 cm tall with creatinine 0.6 gets 0.413 times 120 divided by 0.6, which is 82.6 mL/min/1.73 m2. The constant assumes the creatinine assay is IDMS-traceable, which modern labs are. Staging follows KDIGO: G1 at 90 or above, G2 60 to 89, G3a 45 to 59, G3b 30 to 44, G4 15 to 29, and G5 under 15. Note that G1 and G2 require additional evidence of kidney damage, like proteinuria, to count as CKD; the number alone does not diagnose.
Worked Example
A child 120 cm tall with serum creatinine 0.6 mg/dL has an estimated GFR of 82.6. The calculator places this in stage G2, which without proteinuria or other kidney damage markers is not chronic kidney disease, just a number to watch. If the creatinine later rises to 1.0 at the same height, the eGFR falls to about 50, showing how sensitively the formula tracks creatinine changes.
Reading Your Result
Above 90 with no proteinuria or structural abnormality is normal kidney function. The 60 to 89 band deserves attention to trend and a urine check for protein. Below 60 persisting over 3 months meets CKD criteria and needs nephrology involvement. Under 30 is severe reduction where complications like anemia and bone disease are managed actively, and under 15 is kidney failure. A single eGFR is a snapshot; creatinine fluctuates with hydration, muscle mass, and lab variation, so repeat before reacting to a borderline value.
| eGFR | KDIGO stage | Meaning |
|---|---|---|
| 90+ | G1 | Normal (needs damage marker for CKD) |
| 60-89 | G2 | Mildly decreased, check urine |
| 30-59 | G3a/G3b | Moderate, nephrology care |
| 15-29 | G4 | Severe, prepare for renal replacement |
| Under 15 | G5 | Kidney failure |
Limitations
The Schwartz equation estimates, with real error around measured GFR, and it performs worst at near-normal function where small creatinine changes swing the result. It assumes steady-state creatinine, so it misleads in acute kidney injury where creatinine is still rising. Muscle mass extremes, vegetarian diets, and some medications shift creatinine independent of GFR. Confirm important decisions with repeat labs and nephrology input.
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For informational purposes only, not medical advice. Consult a healthcare professional.
Frequently Asked Questions
What is the Schwartz formula?
eGFR equals 0.413 times height in centimeters divided by serum creatinine in mg/dL. Developed by George Schwartz and colleagues and updated in 2009 with the 0.413 constant calibrated to IDMS-traceable creatinine assays, it is the standard bedside GFR estimate for children from 1 to 17 years.
What is a normal GFR for a child?
Around 90 to 120 mL/min/1.73 m2 after age 2, similar to adults. Newborns start much lower, near 20 to 40, and reach adult levels by about age 2 as the kidneys mature. Always interpret infant values against age-expected norms, not adult cutoffs.
Why does the formula use height?
Height stands in for muscle mass, which determines how much creatinine the body produces each day. Two children with the same true GFR but different muscle mass have different creatinines; dividing by height corrects for that. It is an elegant workaround from before cystatin C existed.
What are the CKD stages in children?
The same KDIGO G1 to G5 stages as adults, based on eGFR: 90+, 60-89, 45-59, 30-44, 15-29, under 15. Stages G1 and G2 only count as CKD with a marker of kidney damage such as albuminuria. Staging guides monitoring frequency and referral timing.
Can dehydration change the eGFR?
Yes. Dehydration raises creatinine and lowers the estimated GFR without any real kidney damage, and rehydration normalizes it. That is why a surprising eGFR gets repeated after addressing volume status before anyone acts on it.
What is cystatin C and is it better?
A protein filtered by the kidneys that estimates GFR independent of muscle mass, useful in children with very high or low muscle mass where creatinine misleads. Combined creatinine-cystatin equations exist but are not bedside-simple. For routine use, Schwartz remains the standard.
Does the formula work for babies under 1?
Less reliably. The 0.413 constant was validated mainly from age 1 upward, and newborn creatinine reflects maternal creatinine in the first days. Neonatal kidney function needs age-specific norms and nephrology guidance, not this calculator.
Why do labs report eGFR for adults automatically but not children?
Adult equations like CKD-EPI use age, sex, and creatinine without height, so labs can compute them from the blood sample alone. Schwartz needs height, which the lab does not have, so pediatric eGFR is calculated at the bedside or in the clinic.
How often should eGFR be checked in CKD?
KDIGO suggests frequency by stage: annually for G1-G2, more often as function falls, up to monthly in G4-G5 or when changing therapy. Trends across consistent labs matter more than single values, and albuminuria is tracked alongside.
Can kidney function improve in children?
Sometimes. Acute injuries can recover substantially, and growth plus good blood pressure and proteinuria control can stabilize chronic disease. The eGFR trend over months tells the story; single values just take its picture.