GFR Calculator
Estimated GFR from serum creatinine using the race-free 2021 CKD-EPI equation, with the KDIGO stage — an estimate to discuss with a clinician, never a diagnosis.
GFR Calculator: with the default inputs, estimated gfr is 89.
From a standard blood panel. Set the units below to match your lab report — 1.0 mg/dL is about 88 µmol/L.
mL/min/1.73 m²
- KDIGO GFR category
- G2
- What that category means
- Mildly decreased
- Non-indexed GFR for your body size
- 101mL/min — the figure some drug-dosing references want, not the one on your lab report.
- Body surface area
- 1.97 m²Du Bois formula.
- Creatinine in mg/dL
- 1
- Share of a typical young-adult GFR
- 74%Against roughly 120 mL/min/1.73 m².
Assumptions
- Uses the 2021 CKD-EPI creatinine equation (Inker et al., NEJM 2021), the race-free revision recommended by the NKF-ASN task force and now standard in the United States.
- Serum creatinine is assumed to be measured by an IDMS-traceable assay, which is standard in modern laboratories.
- The result is indexed to a body surface area of 1.73 m². The non-indexed figure uses the Du Bois BSA formula and is shown only because some drug-dosing references want it.
- The equation assumes a stable creatinine and typical muscle mass for age and sex, so it does not hold in acute kidney injury or at extremes of muscle mass. It was not validated in pregnancy.
- Developed and validated in adults. Children need a paediatric equation such as CKiD U25.
- This is an estimate for information only. It does not diagnose anything, and results belong with a clinician.
| Category | eGFR (mL/min/1.73 m²) | Description | |
|---|---|---|---|
| G1 | 90 and above | Normal or high | |
| G2 | 60–89 | Mildly decreased | ← you |
| G3a | 45–59 | Mildly to moderately decreased | |
| G3b | 30–44 | Moderately to severely decreased | |
| G4 | 15–29 | Severely decreased | |
| G5 | Under 15 | Kidney failure |
G1 and G2 only count as chronic kidney disease when there is other evidence of kidney damage, such as albuminuria, and the abnormality has been present for more than three months.
How this is worked out
The formula
CKD-EPI 2021 creatinine equation (race-free): eGFR = 142 × min(Scr/κ, 1)^α × max(Scr/κ, 1)^(−1.200) × 0.9938^age × 1.012 (if female) Scr = serum creatinine in mg/dL κ = 0.7 (female) or 0.9 (male) α = −0.241 (female) or −0.302 (male) Result in mL/min/1.73 m² µmol/L → mg/dL: divide by 88.4
Open How it’s calculated above to see this worked through with your own numbers.
What you enter
- Serum creatinine
- From a standard blood panel. Set the units below to match your lab report — 1.0 mg/dL is about 88 µmol/L.from 0.01 to 2000 · defaults to 1
- Creatinine units
- Choose one of 2 options.mg/dL (United States) · µmol/L (most other countries)
- Age
- A number.from 18 to 110 · whole numbers only · defaults to 55
- Sex
- Choose one of 2 options.Male · Female
- Height(under More options)
- Optional. Only used to convert the result out of its 1.73 m² normalisation.in ft, in, cm, m · from 3 to 8.5 · defaults to 5.8333
- Weight(under More options)
- A number.in lb, kg, st · from 20 to 1000 · defaults to 175
What you get back
- Estimated GFRmain answer
- mL/min/1.73 m²
- KDIGO GFR category
- What that category means
- Non-indexed GFR for your body size
- mL/min — the figure some drug-dosing references want, not the one on your lab report.
- Body surface area
- Du Bois formula.
- Creatinine in mg/dL
- Share of a typical young-adult GFR
- Against roughly 120 mL/min/1.73 m².
What this assumes
- Uses the 2021 CKD-EPI creatinine equation (Inker et al., NEJM 2021), the race-free revision recommended by the NKF-ASN task force and now standard in the United States.
- Serum creatinine is assumed to be measured by an IDMS-traceable assay, which is standard in modern laboratories.
- The result is indexed to a body surface area of 1.73 m². The non-indexed figure uses the Du Bois BSA formula and is shown only because some drug-dosing references want it.
- The equation assumes a stable creatinine and typical muscle mass for age and sex, so it does not hold in acute kidney injury or at extremes of muscle mass. It was not validated in pregnancy.
- Developed and validated in adults. Children need a paediatric equation such as CKiD U25.
- This is an estimate for information only. It does not diagnose anything, and results belong with a clinician.
About this calculator
This is an estimate, not a diagnosis. It cannot tell you whether you have kidney disease, and a number outside the normal range on this page is a reason to talk to a clinician, not a conclusion. Kidney function is judged from repeated tests, a urine albumin measurement and your history — never from one calculation.
With that said, here is exactly what the calculation is.
What eGFR measures
Glomerular filtration rate is how much blood your kidneys filter per minute. Measuring it directly requires infusing a marker and timing its clearance, which is slow and expensive, so laboratories estimate it from creatinine — a waste product of muscle metabolism that healthy kidneys clear at a fairly steady rate. When filtration falls, creatinine rises.
Because creatinine production depends on muscle mass, the estimating equation has to adjust for the things that predict muscle: age and sex. This calculator uses the 2021 CKD-EPI creatinine equation, published by Inker and colleagues in the New England Journal of Medicine.
Why "race-free" matters
Earlier versions of CKD-EPI multiplied the result by about 1.16 for Black patients. That coefficient came from observed average differences in creatinine, but using race — a social category, self-reported, with no biological boundary — as a variable in a clinical equation systematically reported higher kidney function for Black patients, which delayed referrals, specialist care and transplant waitlisting. A joint National Kidney Foundation and American Society of Nephrology task force recommended dropping it, and the 2021 equation was refit without it. That is the version here, and it is now the US standard.
Reading the result
The KDIGO categories run G1 (90 and above) to G5 (under 15). Two things about them are widely misread:
- G1 and G2 are not diagnoses. An eGFR of 75 with no albuminuria and no other sign of kidney damage is not chronic kidney disease. It is a normal number for many adults, and eGFR declines gently with age in everyone.
- CKD requires three months. A single reduced eGFR is often dehydration, an acute illness, or a drug effect — NSAIDs, some antibiotics, ACE inhibitors after a dose change. The definition of chronic kidney disease requires the abnormality to persist.
Albuminuria matters as much as eGFR. KDIGO stages kidney disease on both axes, and someone with a normal eGFR and heavy albuminuria may be at higher risk than someone with a mildly reduced eGFR and none.
Where the estimate breaks
The equation assumes creatinine production typical for your age and sex. It is unreliable in acute kidney injury and in people with very high or very low muscle mass — KDIGO names bodybuilders, above-knee amputation, spinal cord injury, muscle-wasting disease and class III obesity — as well as with creatine supplementation or a very high-protein diet. It was never validated in pregnancy. It was developed in adults; children need the CKiD U25 or Schwartz equations instead. Where precision matters, guidelines recommend confirming with cystatin C, which does not depend on muscle mass, and the combined creatinine–cystatin C equation is more accurate than either alone.
If a result here worries you, the useful next step is your own lab report and a doctor's appointment.
Frequently asked questions
▸What is a normal GFR?
Around 90–120 mL/min/1.73 m² in healthy young adults, falling gradually with age — a value in the 60s or 70s is common and often normal at 70. On its own, an eGFR above 60 without albuminuria is not kidney disease.
▸Does this diagnose kidney disease?
No. It estimates one number from one blood test. Chronic kidney disease requires the abnormality to persist for over three months and is assessed alongside urine albumin and your medical history, by a clinician.
▸Why did the race coefficient go away?
Because race is a social category, not a biological variable, and applying a multiplier to Black patients reported higher kidney function for them — delaying referral, specialist care and transplant listing. An NKF-ASN task force recommended removal, and the 2021 CKD-EPI equation was refit without it.
▸Should I use cystatin C instead?
Where precision changes a decision — transplant evaluation, drug dosing, an unexpected result — guidelines recommend confirming with cystatin C, which does not depend on muscle mass. The combined creatinine and cystatin C equation is the most accurate of the three.
▸Why does my lab report a different number?
Labs may still use an older equation, or report indexed and non-indexed values differently. Your lab's own figure is the one your clinician will use; this calculator shows you what the current standard equation gives.
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