Dosage Calculator

Formula

Worked Example

1. Multiply out the order. 15 mg/kg × 82 kg = 1,230 mg/day.
2. Apply the ceiling. 1,230 exceeds the 1,000 mg maximum, so the dose is capped at 1,000 mg/day.
3. Divide by frequency. 1,000 ÷ 3 = 333.3 mg per dose.
4. Convert to volume. 250 mg/5 mL = 50 mg/mL, so 333.3 ÷ 50 = 6.67 mL.
5. Check it backwards. 6.67 mL × 50 × 3 ÷ 82 = 12.2 mg/kg/day — below the order because the cap bound.

Strengths & Limits Of This Model

Practical Use Cases

Converting an order into a measurable volume

The step where mg becomes mL is where most administration errors occur.

Checking whether a maximum dose binds

In heavier patients the ceiling frequently overrides the weight-based figure.

Performing an independent second check

Work backwards from the volume to mg/kg/day and confirm it matches the order.

Dosing a child

Paediatric orders have their own conventions. Use the Pediatric Dose Calculator.

Methodology & Editorial Standards

This engine performs the arithmetic that converts a prescribed weight-based order into an administrable quantity, and it enforces the maximum daily dose as part of that conversion rather than reporting it as an afterthought. The daily amount is the lesser of the weight-based product and the stated ceiling, because above a certain body weight the ceiling rather than the arithmetic determines the dose, and a calculator that omits this step will confidently produce an overdose for a heavy patient. The per-dose amount follows from the daily total and the dosing frequency, and the volume follows from the concentration expressed as strength per unit volume. The engine presents an independent reverse check, recomputing milligrams per kilogram per day from the final volume, since verifying a calculation by a different route is standard practice in medicines administration and will reveal both arithmetic slips and an unnoticed cap. Measurement guidance reflects that household spoons vary by nearly threefold and are never an acceptable measure. The engine states the unit conventions whose violation causes thousand-fold errors, and notes that weight-based arithmetic is blind to renal and hepatic clearance. This calculator is an educational estimate and is not medical advice, diagnosis, treatment or a prescription. It performs arithmetic on values you enter and cannot assess your clinical condition. Never start, stop, change or skip a dose of any medicine on the basis of a number produced here. Dose selection belongs to a prescriber working from the approved product label, your full medication list and your current clinical state. If you are acutely unwell, dehydrated, vomiting, or your kidney function is changing, estimating equations are unreliable and urgent clinical review is required. The engine implements the standard published formula for this calculation. Inputs are validated for domain and sign before evaluation, and any undefined case returns an em-dash rather than a spurious value.

Computation runs in IEEE-754 double precision at full internal precision; rounding to two decimal places occurs strictly at the display layer, so no cumulative drift enters the result. All monetary outputs use accounting presentation — grouped thousands, two decimals, negatives in parentheses — so figures can be transcribed directly into a model or working paper. Division-by-zero and out-of-domain inputs return an em-dash rather than a misleading number.

This engine was reconciled against an independent reference implementation and hand-verified for the worked example above before release. Our full five-stage review process is published on the About Us page.

Related Health Engines