Kidney Failure Risk Equation Calculator

What is this?

The Kidney Failure Risk Equation (KFRE) predicts the probability that a person with chronic kidney disease will need dialysis or a kidney transplant within 2 and 5 years. Developed by Tangri and colleagues and validated in over 700,000 people across more than 30 countries, it is the most widely validated kidney failure prediction model in use.

How to Use the Kidney Failure Risk Equation Calculator

The Kidney Failure Risk Equation (KFRE) estimates the probability that a person with chronic kidney disease will need dialysis or a transplant within the next 2 and 5 years. It was developed by Tangri and colleagues and validated in more than 700,000 people across more than 30 countries, which makes it one of the most widely tested prediction models in nephrology.

It answers a narrower question than people often expect. It predicts treated kidney failure - not death, not the speed of eGFR decline, and not whether CKD will progress a stage. Use it for referral and planning decisions, not as a general prognosis.

1. Choose the Model

The 4-variable model needs only age, sex, eGFR and urine albumin-to-creatinine ratio, and performs almost as well as the longer ones. The 6-variable model adds diabetes and hypertension. The 8-variable model adds serum albumin, phosphorus, bicarbonate and calcium. These are three separate published models with their own coefficients, not one model with optional extras, so the same patient will give slightly different answers on each tab. If you have the labs, use the 8-variable; otherwise the 4-variable is the standard choice.

2. Set the Region

The equation is calibrated separately for North American and non-North American populations. For the same patient, risk outside North America came out lower, so choosing the wrong region shifts every number. This is a calibration setting, not a demographic one - pick the region the patient is treated in.

3. Enter eGFR and Urine ACR

eGFR is in mL/min/1.73m². The urine albumin-to-creatinine ratio can be entered in mg/g or mg/mmol and is converted for you. ACR must be greater than zero because the equation uses its logarithm - a value of zero has no logarithm, so the calculator will ask for a real measurement rather than substituting one.

4. Add the Laboratory Values for the 8-Variable Model

Serum albumin, phosphorus and calcium can each be entered in conventional or SI units and are converted for you. Bicarbonate needs no conversion: mEq/L and mmol/L are the same number for a monovalent ion.

5. Read the Result Against the Thresholds

KDIGO 2024 suggests a 5-year risk of 3% to 5% as a trigger for considering nephrology referral, and a 2-year risk of 40% as the point to prepare kidney replacement therapy - modality education, vascular access, and transplant referral. The contribution table shows which factor is driving the number.

Key Formulas Used in the Calculator

The Equation

$\text{Risk} = 1 - S_0^{\exp(L)}$

S0 is the baseline survival for the chosen region and time horizon, and L is the risk score below. A patient exactly average on every factor has L = 0, so exp(L) = 1 and the risk is simply 1 - S0.

Risk Score, 4-Variable Model

$L = -0.2201\left(\frac{\text{Age}}{10}-7.036\right) + 0.2467\left(\text{Male}-0.5642\right) - 0.5567\left(\frac{\text{eGFR}}{5}-7.222\right) + 0.4510\left(\ln(\text{ACR})-5.137\right)$

Age in years, male = 1 and female = 0, eGFR in mL/min/1.73m², and ACR in mg/g. The constants subtracted are the development cohort's means, which is what centres the score on the average patient.

Baseline Survival

$\text{4-variable:}\quad S_0 = \begin{cases} 0.9750\ (2\,\text{yr}),\ 0.9240\ (5\,\text{yr}), & \text{North America} \\ 0.9832\ (2\,\text{yr}),\ 0.9365\ (5\,\text{yr}), & \text{Elsewhere} \end{cases}$

The 8-variable model uses 0.9780 and 0.9301 in North America, 0.9827 and 0.9245 elsewhere. Because risk outside North America is lower for identical covariates, the region setting changes every answer.

Benefits

• All three published models - 4, 6 and 8-variable - with their own coefficients

• North American and international calibration, which shifts every result

• Urine ACR, albumin, phosphorus and calcium accepted in conventional or SI units

• Shows how much each factor contributed to the risk score

• Flags results outside the eGFR range the equation was developed in

• Reads the result against the KDIGO referral and access-planning thresholds

When & Where to Use

• Deciding whether a CKD patient needs nephrology referral

• Timing vascular access creation or transplant referral

• Prioritising a CKD caseload by risk rather than eGFR alone

• Explaining prognosis to a patient in absolute terms

• Comparing risk before and after a change in albuminuria

• Teaching how competing mortality affects a risk model

Who Should Use This Calculator

The Kidney Failure Risk Equation Calculator is for clinicians managing chronic kidney disease - primary care physicians deciding on referral, nephrologists planning kidney replacement therapy, and trainees learning risk-based CKD care. Patients and carers can use it to understand a number a clinician has quoted, but it is not a substitute for that conversation.

Pro Tips

• The KFRE was developed in CKD stages G3-G5, roughly an eGFR of 10 to 59 mL/min/1.73m².

• KDIGO 2024 uses a 5-year risk of 3-5% to guide nephrology referral.

• A 2-year risk of 40% or more is the threshold for preparing vascular access and transplant referral.

• Older age lowers predicted risk because of competing mortality, not because age protects the kidneys.

• The 4-, 6- and 8-variable models are separately fitted, so their answers differ slightly for the same patient.

• It predicts treated kidney failure only - not death, and not the rate of eGFR decline.

• Clinical decision support, not medical advice.