What is GFR and why do doctors use eGFR?

Glomerular filtration rate (GFR) is the volume of plasma filtered through the glomeruli per minute, normalized to body surface area (mL/min/1.73 m²). It is the central measure of kidney function. True measured GFR (inulin or iohexol clearance) is accurate but impractical for routine care, so clinicians use estimated GFR (eGFR) equations based on serum creatinine, age, sex, and sometimes race or height in children. eGFR guides CKD staging, medication dosing (metformin, DOACs, contrast discussions), nephrology referral, and dialysis planning. A single eGFR number is an estimate—trends over months matter more than one borderline value.

Which GFR formula does my lab use—MDRD, CKD-EPI, or Mayo?

Most US and European chemistry labs report CKD-EPI creatinine-based eGFR on routine panels. MDRD is older and tends to underestimate GFR when kidney function is still near normal. This calculator shows MDRD, CKD-EPI (2009 with optional Black race coefficient), and Mayo quadratic side by side so you can see spread. Mayo often reads higher at low creatinine because it floors SCr at 0.8 mg/dL. Your official result is whatever equation your laboratory information system applies—often CKD-EPI 2021 without a race factor since 2021–2023 updates. Do not average formulas for clinical decisions; use your lab’s reported eGFR.

How do I convert creatinine from μmol/L to mg/dL for this calculator?

Select μmol/L in the unit dropdown or divide by 88.4 manually: mg/dL = μmol/L ÷ 88.4. Example: 80 μmol/L ÷ 88.4 ≈ 0.90 mg/dL. Units must match your lab report. Extreme hemolysis, certain drugs, and very high protein intake can affect creatinine independent of true GFR.

What GFR is considered normal?

In young adults, population mean eGFR is often roughly 90–120 mL/min/1.73 m², with men slightly higher than women on average. KDIGO does not label CKD by GFR alone until values are persistently abnormal with other criteria. An eGFR ≥60 mL/min/1.73 m² without albuminuria or structural damage is frequently adequate for daily function, but a large drop from your personal baseline (for example 95 → 62) can still warrant evaluation. Age-related decline after the fourth decade is common; equations bake in age so a “lower normal” eGFR at 75 may still be expected for that age.

What are the CKD GFR stages (G1–G5)?

KDIGO stages kidney function by GFR: G1 ≥90, G2 60–89, G3a 45–59, G3b 30–44, G4 15–29, G5 <15 mL/min/1.73 m². Staging also uses albuminuria (A1–A3) and cause of disease. This page’s simplified teaching label averages adult MDRD, CKD-EPI, and Mayo into one band (for example “CKD3 Moderate”)—your clinician uses persistent lab trends plus urine albumin-to-creatinine ratio, imaging, and history. CKD is diagnosed when abnormalities persist ≥3 months unless biopsy-proven sooner.

Why do MDRD, CKD-EPI, and Mayo give different numbers on the same inputs?

Each equation was derived from different cohorts and math forms. MDRD uses a single power law on creatinine; CKD-EPI uses piecewise exponents above/below sex-specific creatinine thresholds; Mayo uses an exponential quadratic form with a creatinine floor. At SCr 0.9 mg/dL and age 50 (male, not Black), you might see MDRD ~89, CKD-EPI ~99, Mayo ~120—spread widens when creatinine is low-normal. Laboratories pick one reporting standard; comparing three here is educational transparency, not a recommendation to average them for prescribing.

What is the race coefficient in MDRD and CKD-EPI?

Older equations multiplied eGFR by ~1.212 (MDRD) or used higher constants (CKD-EPI) for patients identified as Black, reflecting calibration in development cohorts. That approach is controversial and being removed from clinical reporting: CKD-EPI 2021 and creatinine 2021 equations without race are increasingly standard because race is a social construct, not a biologic GFR determinant. This calculator retains the legacy toggle for education and comparison with historical lab values. For new clinical decisions, follow your lab’s current race-free eGFR if available.

How does muscle mass affect creatinine and GFR estimates?

Creatinine is generated from muscle creatine metabolism. A muscular athlete with SCr 1.2 mg/dL may have higher true GFR than a frail older adult with the same SCr. Low muscle mass (sarcopenia, amputation, malnutrition) can mask kidney failure because SCr stays “normal” while true GFR falls—cystatin C–based eGFR is sometimes added in that scenario. Acute kidney injury, hydration, and high meat intake can shift SCr faster than chronic GFR changes. Interpret eGFR with context, not in isolation.

When should I use the Schwartz formula (pediatric mode)?

For patients ≤18 years, height-based Schwartz is a classic bedside estimate: GFR = 0.413 × height(cm) / SCr(mg/dL). Enter height in cm or inches and serum creatinine. Example on this page: height 110 cm, SCr 0.9 mg/dL → eGFR ≈ 50 mL/min/1.73 m² (CKD3 teaching band). Neonates, obesity, and chronic illness may need updated coefficients or cystatin C per pediatric nephrology. Adult MDRD/CKD-EPI are not validated under age 18.

Can a low GFR be reversed?

Sometimes. Dehydration, ACE inhibitor/ARB initiation, NSAIDs, contrast injury, obstruction, or infection can cause reversible creatinine rises—treat the cause and recheck in days to weeks. Chronic CKD from diabetes or hypertension usually shows gradual decline; goals are blood pressure, glycemic control, SGLT2 inhibitors where indicated, and slowing progression—not expecting full normalization. Sudden large drops or symptoms (fluid overload, hyperkalemia, uremic nausea) need urgent medical evaluation.

How is GFR measured accurately in research or specialty care?

Measured GFR uses exogenous markers (inulin, iohexol, iothalamate) with timed urine or plasma clearance. It is the reference standard but needs infusion or multiple samples. Creatinine clearance from 24-hour urine overestimates GFR ~10–20% because creatinine is secreted in the tubules. eGFR equations approximate measured GFR well enough for population screening but can misclassify individuals at GFR borders.

Is this GFR calculator medical advice?

No. It performs published estimating equations for learning and self-checks against lab reports. CKD diagnosis, medication changes, contrast procedures, and dialysis timing require licensed clinicians and your official laboratory eGFR. Seek emergency care for chest pain, severe shortness of breath, inability to urinate, or confusion with known kidney disease.

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Q: Why do MDRD, CKD-EPI, and Mayo give different numbers on the same inputs?

Each equation was derived from different cohorts and math forms. MDRD uses a single power law on creatinine; CKD-EPI uses piecewise exponents above/below sex-specific creatinine thresholds; Mayo uses an exponential quadratic form with a creatinine floor. At SCr 0.9 mg/dL and age 50 (male, not Black), you might see MDRD ~89, CKD-EPI ~99, Mayo ~120—spread widens when creatinine is low-normal. Laboratories pick one reporting standard; comparing three here is educational transparency, not a recommendation to average them for prescribing.

Q: What is the race coefficient in MDRD and CKD-EPI?

Older equations multiplied eGFR by ~1.212 (MDRD) or used higher constants (CKD-EPI) for patients identified as Black, reflecting calibration in development cohorts. That approach is controversial and being removed from clinical reporting: CKD-EPI 2021 and creatinine 2021 equations without race are increasingly standard because race is a social construct, not a biologic GFR determinant. This calculator retains the legacy toggle for education and comparison with historical lab values. For new clinical decisions, follow your lab’s current race-free eGFR if available.

Q: How does muscle mass affect creatinine and GFR estimates?

Creatinine is generated from muscle creatine metabolism. A muscular athlete with SCr 1.2 mg/dL may have higher true GFR than a frail older adult with the same SCr. Low muscle mass (sarcopenia, amputation, malnutrition) can mask kidney failure because SCr stays “normal” while true GFR falls—cystatin C–based eGFR is sometimes added in that scenario. Acute kidney injury, hydration, and high meat intake can shift SCr faster than chronic GFR changes. Interpret eGFR with context, not in isolation.

Q: When should I use the Schwartz formula (pediatric mode)?

For patients ≤18 years, height-based Schwartz is a classic bedside estimate: GFR = 0.413 × height(cm) / SCr(mg/dL). Enter height in cm or inches and serum creatinine. Example on this page: height 110 cm, SCr 0.9 mg/dL → eGFR ≈ 50 mL/min/1.73 m² (CKD3 teaching band). Neonates, obesity, and chronic illness may need updated coefficients or cystatin C per pediatric nephrology. Adult MDRD/CKD-EPI are not validated under age 18.

Q: Can a low GFR be reversed?

Sometimes. Dehydration, ACE inhibitor/ARB initiation, NSAIDs, contrast injury, obstruction, or infection can cause reversible creatinine rises—treat the cause and recheck in days to weeks. Chronic CKD from diabetes or hypertension usually shows gradual decline; goals are blood pressure, glycemic control, SGLT2 inhibitors where indicated, and slowing progression—not expecting full normalization. Sudden large drops or symptoms (fluid overload, hyperkalemia, uremic nausea) need urgent medical evaluation.

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Nephrology & lab interpretation

GFR Calculator

Estimate glomerular filtration rate (eGFR) in mL/min/1.73 m² from serum creatinine. Adults see MDRD, CKD-EPI (2009), and Mayo quadratic; children see Schwartz (height + creatinine). Educational—labs often report race-free CKD-EPI 2021, which may differ slightly. More tools on our medical calculators hub.

Last updated: June 4, 2026

mg/dL or μmol/L creatinine units

Side-by-side formula comparison for adults

KDIGO-style GFR stage teaching bands

GFR Calculator

Estimate Glomerular Filtration Rate using multiple formulas

Calculator Type

Serum Creatinine (S_Cr)

Age

Must be 18 years or older

Gender

Race

GFR Results

MDRD Study Equation

89 mL/min/1.73 m²

CKD-EPI Formula

99 mL/min/1.73 m²

Mayo Quadratic Formula

120 mL/min/1.73 m²

Average GFR

103 mL/min/1.73 m²

Estimated CKD Stage

Normal or CKD1

Important Notes:

• GFR values are estimates and should be interpreted by a healthcare professional
• Normal GFR: 100-130 mL/min/1.73 m² (men), 90-120 mL/min/1.73 m² (women under 40)
• GFR decreases with age after 40
• Multiple formulas provide different estimates; consult your doctor for interpretation

Example results (from calculator logic)

Near-normal adult

SCr 0.9, age 50, male

CKD-EPI 99

MDRD 89 · Mayo 120 · avg 103

Normal or CKD1

CKD3 range

SCr 2.0, age 65, male

~34

CKD3 (Moderate)

Kidney failure band

SCr 5.0, age 70, female

CKD5 (Kidney Failure)

Pediatric Schwartz

110 cm, SCr 0.9

CKD3 (Moderate)

KDIGO GFR stages (mL/min/1.73 m²)

Stage	GFR	Clinical meaning (summary)
G1 — Normal/high	≥90	Normal unless other markers of kidney damage
G2 — Mild decrease	60–89	Mildly decreased; often stable for years with care
G3a — Mild–moderate	45–59	Moderate decrease; nephrology referral thresholds vary
G3b — Moderate–severe	30–44	More complications; medication dose review common
G4 — Severe	15–29	Plan for renal replacement therapy education
G5 — Kidney failure	<15	Dialysis or transplant planning when symptomatic/indicated

Full CKD classification also requires albuminuria (A1–A3) and cause. This page’s simplified label uses averaged adult formulas only.

Which eGFR formula when? (comparison)

Formula	Inputs	Strength	Caveat
CKD-EPI (2009, with race)	SCr, age, sex, Black/non-Black	Better at higher GFR; widely used on lab reports historically	Many labs now use 2021 race-free CKD-EPI—values may differ from this page
MDRD (IDMS-traceable)	SCr, age, sex, Black/non-Black	Developed in CKD populations; underestimates at high GFR	Still taught; less preferred than CKD-EPI for general screening
Mayo quadratic	SCr (floor 0.8), age, sex	Useful in transplant candidacy teaching contexts	Can read higher than MDRD/CKD-EPI when SCr is low-normal
Schwartz (pediatric)	Height (cm), SCr	Standard bedside pediatric estimate on this page	Updated Schwartz variants exist in specialty references

Population mean estimated GFR by age

Age	Mean eGFR (mL/min/1.73 m²)
20–29	116
30–39	107
40–49	99
50–59	93
60–69	85
70+	75

Equations implemented on this page

MDRD (IDMS-traceable)

GFR = 175 × (S_Cr)^−1.154 × (age)^−0.203 × (0.742 if female) × (1.212 if Black)

CKD-EPI (2009, piecewise by sex & race)

Separate exponents when SCr is below vs above 0.7 (F) or 0.9 (M) mg/dL

Constants 141/144 (non-Black) and 163/166 (Black) with age factor 0.993^age—see calculator for full branches.

Mayo quadratic

If S_Cr < 0.8, use 0.8 · GFR = exp(1.911 + 5.249/S_Cr − 2.114/S_Cr² − 0.00686×age − 0.205 if female)

Schwartz (pediatric)

GFR = 0.413 × height(cm) / S_Cr(mg/dL)

What this GFR calculator covers

Adult eGFR trio

MDRD · CKD-EPI · Mayo

See how legacy equations diverge—especially when creatinine is low-normal.

Pediatric Schwartz

Height-based

Standard teaching formula for children using height and serum creatinine.

CKD stage hint

Teaching band only

Simplified G1–G5 label from averaged adult eGFR or Schwartz in pediatric mode—not a diagnosis.

References

Not for prescribing or diagnosis. Use your laboratory’s official eGFR and clinician guidance for medications, contrast, and dialysis decisions. Emergency symptoms with kidney disease need urgent care.

Frequently Asked Questions

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For nursing students, patients comparing lab eGFR, and nephrology education

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Suggested hashtags: #GFR #KidneyHealth #Nephrology #eGFR #Calculator

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Nephrology & lab interpretation

GFR Calculator

Last updated: June 4, 2026

mg/dL or μmol/L creatinine units

Side-by-side formula comparison for adults

KDIGO-style GFR stage teaching bands

GFR Calculator

Estimate Glomerular Filtration Rate using multiple formulas

Calculator Type

Serum Creatinine (S_Cr)

Age

Must be 18 years or older

Gender

Race

GFR Results

MDRD Study Equation

89 mL/min/1.73 m²

CKD-EPI Formula

99 mL/min/1.73 m²

Mayo Quadratic Formula

120 mL/min/1.73 m²

Average GFR

103 mL/min/1.73 m²

Estimated CKD Stage

Normal or CKD1

Important Notes:

• GFR values are estimates and should be interpreted by a healthcare professional
• Normal GFR: 100-130 mL/min/1.73 m² (men), 90-120 mL/min/1.73 m² (women under 40)
• GFR decreases with age after 40
• Multiple formulas provide different estimates; consult your doctor for interpretation

Example results (from calculator logic)

Near-normal adult

SCr 0.9, age 50, male

CKD-EPI 99

MDRD 89 · Mayo 120 · avg 103

Normal or CKD1

CKD3 range

SCr 2.0, age 65, male

~34

CKD3 (Moderate)

Kidney failure band

SCr 5.0, age 70, female

CKD5 (Kidney Failure)

Pediatric Schwartz

110 cm, SCr 0.9

CKD3 (Moderate)

KDIGO GFR stages (mL/min/1.73 m²)

Stage	GFR	Clinical meaning (summary)
G1 — Normal/high	≥90	Normal unless other markers of kidney damage
G2 — Mild decrease	60–89	Mildly decreased; often stable for years with care
G3a — Mild–moderate	45–59	Moderate decrease; nephrology referral thresholds vary
G3b — Moderate–severe	30–44	More complications; medication dose review common
G4 — Severe	15–29	Plan for renal replacement therapy education
G5 — Kidney failure	<15	Dialysis or transplant planning when symptomatic/indicated

Full CKD classification also requires albuminuria (A1–A3) and cause. This page’s simplified label uses averaged adult formulas only.

Which eGFR formula when? (comparison)

Formula	Inputs	Strength	Caveat
CKD-EPI (2009, with race)	SCr, age, sex, Black/non-Black	Better at higher GFR; widely used on lab reports historically	Many labs now use 2021 race-free CKD-EPI—values may differ from this page
MDRD (IDMS-traceable)	SCr, age, sex, Black/non-Black	Developed in CKD populations; underestimates at high GFR	Still taught; less preferred than CKD-EPI for general screening
Mayo quadratic	SCr (floor 0.8), age, sex	Useful in transplant candidacy teaching contexts	Can read higher than MDRD/CKD-EPI when SCr is low-normal
Schwartz (pediatric)	Height (cm), SCr	Standard bedside pediatric estimate on this page	Updated Schwartz variants exist in specialty references

Population mean estimated GFR by age

Age	Mean eGFR (mL/min/1.73 m²)
20–29	116
30–39	107
40–49	99
50–59	93
60–69	85
70+	75

Equations implemented on this page

MDRD (IDMS-traceable)

GFR = 175 × (S_Cr)^−1.154 × (age)^−0.203 × (0.742 if female) × (1.212 if Black)

CKD-EPI (2009, piecewise by sex & race)

Separate exponents when SCr is below vs above 0.7 (F) or 0.9 (M) mg/dL

Constants 141/144 (non-Black) and 163/166 (Black) with age factor 0.993^age—see calculator for full branches.

Mayo quadratic

If S_Cr < 0.8, use 0.8 · GFR = exp(1.911 + 5.249/S_Cr − 2.114/S_Cr² − 0.00686×age − 0.205 if female)

Schwartz (pediatric)

GFR = 0.413 × height(cm) / S_Cr(mg/dL)

What this GFR calculator covers

Adult eGFR trio

MDRD · CKD-EPI · Mayo

See how legacy equations diverge—especially when creatinine is low-normal.

Pediatric Schwartz

Height-based

Standard teaching formula for children using height and serum creatinine.

CKD stage hint

Teaching band only

Simplified G1–G5 label from averaged adult eGFR or Schwartz in pediatric mode—not a diagnosis.

References

Frequently Asked Questions

Share this calculator

For nursing students, patients comparing lab eGFR, and nephrology education

Share This Calculator

Help others discover this useful tool

Copy Link

Share on Social Media

X Facebook LinkedIn WhatsApp

Share via Email

Suggested hashtags: #GFR #KidneyHealth #Nephrology #eGFR #Calculator

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Cockcroft–Gault and urine-based clearance estimates for drug dosing education.

Use Calculator

Kidney Disease Progression Calculator

Educational modeling of eGFR decline over time with risk factors.

Use Calculator

Kidney Stone Risk Calculator

Metabolic risk factors related to renal stone disease.

Use Calculator

Osmolality Calculator

Serum osmolality estimate from sodium, glucose, and BUN.

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Acid–base and electrolyte pattern recognition.

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