Carboplatin Dose Calculator (AUC / Calvert Formula)

What the Calvert formula calculates

The Calvert formula determines the total carboplatin dose needed to achieve a specific area under the plasma concentration-time curve (AUC), the pharmacokinetic target that best correlates with both efficacy and toxicity. The formula is: Dose (mg) = Target AUC x (GFR + 25). The constant 25 mL/min represents the non-renal clearance of carboplatin (tubular secretion and protein binding). Because carboplatin is primarily eliminated by the kidneys, knowing a patient's actual kidney function is essential for accurate dosing. AUC-based dosing replaced older body surface area (BSA) approaches in most guidelines because it accounts for individual variation in renal clearance that BSA cannot capture.

How GFR is estimated with the Cockcroft-Gault equation

The Cockcroft-Gault (CG) equation estimates creatinine clearance (used as a GFR proxy) from serum creatinine, age, body weight, and sex. For men: GFR = ((140 - Age) x Weight) / (72 x Serum Creatinine). For women, the result is multiplied by 0.85. Three body weight choices exist: actual body weight (ABW) for patients at or near ideal weight, ideal body weight (IBW, calculated by the Devine formula) for underweight patients, and adjusted body weight (ABW = IBW + 0.4 x (Actual - IBW)) for obese patients (actual weight > 120% of IBW). Using actual weight in obese patients overestimates GFR and leads to overdosing; this calculator defaults to the adjusted method and switches automatically. The FDA recommends capping estimated GFR at 125 mL/min because creatinine-based estimates become unreliable at very high filtration rates, and the Calvert formula can produce doses higher than intended.

Serum creatinine floor and edge cases

In patients with very low muscle mass (for example, elderly, cachectic, or debilitated patients), serum creatinine can fall below 0.7 mg/dL. An abnormally low creatinine artificially inflates the CG estimate, so this calculator floors the value at 0.7 mg/dL in line with standard clinical practice and FDA labeling guidance. For patients with unstable creatinine, who are undergoing dialysis, or whose GFR falls below 15-20 mL/min, the Calvert formula is not recommended and actual measured creatinine clearance (EDTA GFR or 24-hour urine collection) should be used instead. For target AUC above 6 mg/mL/min, measured clearance is also strongly preferred.

Clinical interpretation and dose adjustment

After the first cycle, subsequent carboplatin doses may be adjusted based on hematologic nadir. A post-treatment platelet count above 100,000/mcL typically supports dose escalation to 125% of the prior dose; counts of 50,000 to 100,000/mcL support no change; and counts below 50,000/mcL warrant dose reduction to 75%. Carboplatin causes cumulative myelosuppression, so patients with prior platinum exposure, prior radiation, or baseline cytopenias generally receive lower target AUC values (4-5 mg/mL/min) compared with treatment-naive patients (5-7 mg/mL/min). The dose printed by this calculator is an estimate for clinical reference; it must be verified against your institutional protocol and reviewed by an oncology pharmacist before administration.