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Antibiotic Dose By Weight Calculator

Work out antibiotic dose by weight instantly with clear inputs, formula shown and shareable results.

About Antibiotic Dose By Weight Calculator

Converts a mg/kg/day antibiotic prescription into per-dose amounts and applies the stated adult maximum where the weight-based figure would exceed it.

Formula

Divided daily dosing

Daily dose = min(weight x mg/kg/day, maximum); per dose = daily dose / doses per day

Worked example

With the default values below, Antibiotic Dose By Weight Calculator returns Dose per administration of 1,167. Change any input above and every figure here is recalculated in your browser.

Inputs used

Body weightaccepts 1–250 kg
70 kg
Total daily doseaccepts 1–400 mg/kg/day
50 mg/kg/day
Doses per dayaccepts 1–6
3
Maximum daily doseaccepts 100–20,000 mg
4,000 mg

Results

Dose per administration
1,167 mg
Daily dose after any cap
3,500 mg
Weight-based daily dose
3,500 mg
Cap status
Weight-based dose used

Step by step

  1. 1Values used
  2. 2Divided daily dosing
  3. 3Dose per administration= 1,167 mg
  4. 4Daily dose after any cap= 3,500 mg
  5. 5Weight-based daily dose= 3,500 mg
  6. 6Cap status= Weight-based dose used

Assumptions and limits

  • The result is derived only from the 4 inputs listed above. Anything not among them is not part of the calculation.
  • In particular, this calculator does not take inflation, tax, fees or charges or compounding frequency into account.
  • Figures are rounded for display to whole numbers, so totals built from several rounded parts can differ slightly from the unrounded arithmetic.
  • Educational estimate only. Not a substitute for professional clinical judgement, and must not be used to make treatment or dosing decisions.
  • This is an estimate for general information and not professional medical advice. See the full disclaimer for the limits that apply to this kind of calculator.

How these calculators are built and tested is described on the Methodology page. If a figure looks wrong, please report it.

Educational estimate only. Not a substitute for professional clinical judgement, and must not be used to make treatment or dosing decisions.

Frequently Asked Questions

Why cap the dose?

Weight-based dosing in large adults and adolescents can exceed licensed maxima, which are set on safety data.

Do all antibiotics divide evenly?

No. Some regimens use a larger first dose or unequal intervals; follow the specific protocol.

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