Inputs
Example data table
These are illustrative inputs only. They are not recommendations.
| Age | Sex | Weight (kg) | Height (cm) | Basis | Value | Renal% | Hepatic% | Cap (mg) | Round (mg) | Output (mg) |
|---|---|---|---|---|---|---|---|---|---|---|
| 45 | Male | 78 | 175 | mg/m² | 20 | 100 | 100 | — | 2.5 | ~35.0 |
| 62 | Female | 60 | 160 | mg/kg | 0.3 | 75 | 100 | — | 1 | ~14 |
| 30 | Male | 90 | 182 | Flat mg | 25 | 100 | 100 | 20 | 1 | 20 |
Formula used
- BSA (Mosteller): BSA = √((Height_cm × Weight_kg) / 3600)
- Base dose: mg/m² × BSA, or mg/kg × Weight, or Flat mg
- Adjusted dose: Base × (Renal%/100) × (Hepatic%/100)
- Dose cap: min(Adjusted, MaxDose)
- Rounding: round(Capped / Increment) × Increment
- CrCl (Cockcroft–Gault): ((140 − Age) × Weight) / (72 × SCr); ×0.85 if female
How to use this calculator
- Enter patient age, sex, weight, and height.
- Select the regimen basis used in your protocol.
- Type the protocol’s dose value exactly as written.
- Apply renal/hepatic adjustment factors per your guideline.
- Optionally add a max cap and rounding increment.
- Press Calculate and review the step-by-step output.
- Export CSV or PDF for independent double-checking.
Dose basis selection
Methotrexate dosing protocols often scale exposure using body surface area or weight while balancing efficacy and toxicity risk. This calculator supports BSA via the Mosteller method, weight based dosing, and flat dose entries. It also displays creatinine clearance using Cockcroft–Gault to document renal context. Results appear stepwise so a second checker can reproduce the arithmetic from identical inputs and confirm the same outcome and compare with the written order very carefully.
Body surface area sensitivity
BSA depends on both height and weight, so small measurement differences can shift the final dose, especially with higher mg per square meter regimens. A 5% weight change may move BSA by roughly 2% to 3% in many adults. Recording units consistently and using recently measured values reduces error. The tool keeps intermediate values visible, supporting audit trails in verification workflows Note whether the dosing weight should be actual, ideal, or adjusted.
Adjustment factor transparency
Renal and hepatic adjustment factors vary widely by indication, route, and local guidance. Rather than embedding one rule, the calculator accepts percentage factors so teams can mirror their approved protocol. A renal factor of 75% means the adjusted dose is multiplied by 0.75 before any cap or rounding step. This approach avoids hidden assumptions and encourages explicit documentation of modifiers Enter the chosen factors exactly as your guideline specifies for patients.
Capping and rounding controls
Dose caps and rounding increments are controls that improve safety and preparation. A cap can prevent unintended escalation when BSA is unusually high or when a dose value was entered with the wrong unit. Rounding to an increment aligns with vial strengths, syringe markings, or infusion pump programming. The report shows both capped and rounded outputs so clinicians can confirm feasibility before administration Rounding rules should match setting, strengths, and devices used.
Export-ready double-checking
Export features help teams communicate calculations without transcription. CSV captures inputs, derived BSA and clearance, and each dose stage for attachment to notes or double check logs. PDF provides a portable summary with review flags for out of range entries. Even with automation, independent verification remains essential; always reconcile with the order, laboratory results, route, timing, and the current treatment plan Store exports with timestamped labs to support later reconciliation and review.
FAQs
1) What does this tool calculate?
It calculates a base dose from BSA, weight, or a flat value, then applies optional renal and hepatic percentage factors, an optional maximum cap, and an optional rounding increment. It also reports BSA and creatinine clearance for documentation.
2) Which BSA formula is used?
It uses the Mosteller method: BSA = √((height_cm × weight_kg) / 3600). This is commonly used because it is simple and closely matches more complex formulas for many adults and children.
3) Does the tool decide the correct adjustment factor?
No. Adjustment rules differ by protocol and indication. The tool accepts factors as percentages so you can enter the values required by your local guideline, then see their impact transparently in the step-by-step result.
4) Why are capping and rounding included?
Capping can limit unexpected dose inflation, and rounding can align the final dose with vial strengths or administration constraints. The report shows pre-cap, capped, and rounded values so reviewers can verify each step.
5) How should creatinine clearance be interpreted here?
Creatinine clearance is shown using Cockcroft–Gault to provide renal context for verification. Use the weight and serum creatinine approach specified in your protocol, and interpret results alongside labs, hydration status, and clinical judgement.
6) Can I use the exports as the official medication record?
Exports are intended for calculation review and double-check documentation. Always reconcile exported values with the written order, route, schedule, lab results, and your institution’s policies before dispensing or administering medication.