Antibiotic Dosage Calculator

Templates are starting points only. Always verify dose parameters.

Formula Used

This calculator supports three common biological scaling models used in dosing research and practice:

• Weight-based: Dose(mg) = Weight(kg) × (mg/kg/dose)
• Surface-area: Dose(mg) = BSA(m²) × (mg/m²/dose) with Mosteller: BSA = √(Height(cm) × Weight(kg) / 3600)
• Fixed-dose: Dose(mg) = Fixed mg per dose

Modifiers are then applied:

• AdjustedDose = BaseDose × SeverityFactor × RenalFactor
• DosesPerDay = 24 / IntervalHours
• DailyTotal = AdjustedDose × DosesPerDay
• CourseTotal = DailyTotal × DurationDays
• mL per dose = AdjustedDose / Concentration(mg/mL) (if provided)

How to Use This Calculator

1. Enter weight (required). Add height if you want BSA estimation.
2. Select a template or choose Custom and enter dose parameters.
3. Pick dose basis: mg/kg, mg/m², or fixed mg per administration.
4. Set interval hours, start time, and treatment duration.
5. Optionally enter renal data; adjust sensitivity or override factor.
6. Press Calculate to view results above the form, then export.

Example Data Table

Example rows illustrate structure only; not clinical recommendations.

Dose scaling and biological variability

Dose response changes with body size and tissue distribution. Weight-based dosing (mg/kg) suits many beta‑lactams and common pediatrics, while surface-area dosing (mg/m²) can better track metabolic capacity in select protocols. The calculator also estimates BSA using Mosteller: √(height×weight/3600). Seeing both bases side‑by‑side highlights how a 20 kg child and a 70 kg adult can produce different mg totals under the same parameter.

Interval planning and exposure targets

For time‑dependent agents, maintaining concentrations above MIC often matters more than high peaks. Shorter intervals (q6–q8h) increase doses per day (24/interval) and raise daily totals even when mg per dose is unchanged. The time badges display evenly spaced administrations from your start time, supporting adherence planning, nursing shifts, and missed‑dose recovery decisions.

Renal function adjustments in practice

Many antibiotics are renally cleared, so reduced clearance can increase exposure. When renal adjustment is enabled, the tool can use a direct value or estimate with Cockcroft–Gault for adults and Schwartz for children. Educational bands (≥90, 60–89, 30–59, 15–29, <15 mL/min) map to factors, then sensitivity (0–1) blends between no adjustment and full banding to mimic drug‑specific renal dependence.

Rounding for measurable doses

Real dosing requires measurable units. Tablets come in fixed strengths and syringes measure in tenths of a milliliter. Rounding mg per dose to 1–25 mg steps can match available strengths, while rounding mL per dose to 0.1–0.5 mL supports repeatable caregiver technique. The calculator rounds after modifiers, so renal or severity changes still land on practical values.

Liquid concentration and volume conversion

Suspensions and reconstituted solutions are labeled in mg/mL. After computing adjusted mg per dose, the calculator converts to volume using Volume = Dose ÷ Concentration and displays both together. This helps catch mismatches, such as a volume exceeding 10 mL for a small child or an implausibly tiny volume that risks under‑measurement. Entering concentration also allows a dose‑volume cross‑check during dispensing.

Exportable documentation and review

Dose calculations are often rechecked during transitions of care. One‑click CSV exports a tidy field/value summary for spreadsheets, while PDF produces a printable note with modifiers, totals, and scheduled times. Consistent exports support peer review, reduce arithmetic drift between clinicians, and provide an audit trail when parameters change. The Plotly bar chart offers a quick visual comparison of per‑dose, per‑day, and course totals. It also highlights outliers that deserve manual review.

FAQs

1) Does this calculator prescribe a specific antibiotic?

No. It performs dose arithmetic from your inputs and optional templates. Selection, indication, and final dosing must follow official references, local susceptibility data, and clinician judgment.

2) When should I choose mg/kg versus mg/m²?

mg/kg is common for many infections and pediatrics. mg/m² may be used where surface area better reflects physiologic scaling. Use the approach specified by the reference you are following.

3) How is the renal factor applied?

The tool estimates or accepts a renal value, assigns an educational band, then applies a dose multiplier. Sensitivity blends the adjustment to reflect renal dependence differences among drugs, and you can override the factor manually.

4) Why are my daily totals changing with interval?

Doses per day equal 24 divided by interval hours. Shorter intervals increase administrations per day, which increases daily totals even when the mg per dose stays constant.

5) How do I calculate mL per dose for liquids?

Enter concentration in mg/mL. The calculator computes mL per dose as mg per dose divided by mg/mL, then rounds to your chosen increment for easier measurement.

6) What do the CSV and PDF exports include?

Exports capture patient inputs, modifiers, per‑dose and daily totals, course totals, concentration conversions, and suggested times. Use them for review, documentation, and comparison across scenarios.