De-index eGFR to absolute mL/min using body surface area, estimate Cockcroft-Gault creatinine clearance, and compare both kidney function estimates.

Indexed eGFR can be de-indexed for body size, but that result is not the same measurement as creatinine clearance.

Enter the lab-reported value in mL/min/1.73 m².

Used with height to calculate body surface area.

References / Guidelines (for further reading)

  • National Kidney Foundation (NKF): eGFR and kidney function overview pages.
  • KDIGO: chronic kidney disease guideline overview materials.
  • NIDDK or Mayo Clinic: patient education on eGFR/creatinine testing.
  • Medication labeling (FDA/your country’s regulator): renal dosing sections often specify whether to use Cockcroft–Gault CrCl vs eGFR.
Medical disclaimer: Educational use only; not medical advice. Do not use these estimates to start/stop/change medicines or to make diagnosis/dosing decisions—follow medication labeling and consult a clinician/pharmacist. The “Indexed ↔ Absolute GFR” tab is a BSA scaling conversion (not a measured urine creatinine clearance). The Cockcroft–Gault tab is intended for adults with stable kidney function and may be unreliable in rapidly changing creatinine/AKI, pregnancy, dialysis, pediatrics, amputations, edema, or very low/high muscle mass/extreme body size. Many renal drug-dosing recommendations use Cockcroft–Gault CrCl rather than eGFR—confirm which value is required for your situation.
Last reviewed: 2026-01-01

Indexed GFR To Absolute (Unindexed) GFR Formula

The following formula is used to convert a BSA-indexed GFR (mL/min/1.73m²) into an absolute (unindexed) GFR (mL/min) using the patient’s body surface area (BSA). This conversion is not the same as a measured urine creatinine clearance.

GFRabsolute = (GFRindexed × BSA) / 1.73

Variables:

  • GFRabsolute is the absolute (unindexed) GFR (mL/min)
  • GFRindexed is the BSA-indexed GFR (mL/min/1.73m²)
  • BSA is the body surface area (m²)

To calculate the absolute (unindexed) GFR, multiply the indexed GFR by the body surface area, then divide by 1.73 (the standard BSA used for indexing).

Indexed GFR to Absolute (Unindexed) GFR Conversion Table (GFRabsolute = GFRindexed × BSA / 1.73)
GFR (mL/min/1.73m²) Absolute GFR at BSA 1.50 m² (mL/min) Absolute GFR at BSA 1.73 m² (mL/min) Absolute GFR at BSA 2.00 m² (mL/min)
1513.01517.3
2017.32023.1
2521.72528.9
3026.03034.7
3530.33540.5
4034.74046.2
4539.04552.0
5043.45057.8
5547.75563.6
6052.06069.4
6556.46575.1
7060.77080.9
7565.07586.7
8069.48092.5
8573.78598.3
9078.090104.0
9582.495109.8
10086.7100115.6
11095.4110127.2
120104.0120138.7
Formula: Absolute GFR (mL/min) = Indexed GFR (mL/min/1.73m²) × (BSA (m²) / 1.73). Values rounded to one decimal place.

What Is Indexed GFR vs. Creatinine Clearance?

GFR (glomerular filtration rate) describes how much fluid the kidneys filter per unit time. Many lab-reported eGFR values are indexed to a standard body surface area of 1.73 m² (reported as mL/min/1.73m²) so results can be compared across people of different sizes.

Creatinine clearance (CrCl) is different: it is typically measured from urine collection (e.g., 24-hour urine) or estimated from serum creatinine using formulas such as Cockcroft–Gault. CrCl and GFR are related but not interchangeable; CrCl often overestimates true GFR due to creatinine tubular secretion.

How to Convert Indexed GFR to Absolute (Unindexed) GFR

The following steps outline how to convert a BSA-indexed GFR to an absolute (unindexed) GFR.

  1. Determine the indexed GFR in mL/min/1.73m².
  2. Determine the patient’s BSA in m².
  3. Use the formula from above: Absolute GFR = (Indexed GFR × BSA) / 1.73.
  4. Calculate the absolute (unindexed) GFR in mL/min.
  5. Check your answer with the calculator above.

Example Problem:

Use the following variables as an example problem to test your knowledge.

Indexed GFR = 80 mL/min/1.73m²

BSA = 1.8 m²

Absolute (unindexed) GFR = (80 × 1.8) / 1.73 = 83.24 mL/min (≈ 83.2 mL/min)