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Dosage Calcs

Calculators

Weight-Based Dose Calculator

Multiply an ordered dose per kilogram by the patient's weight. Pounds are converted to kilograms first, and every step is shown.

Weight-Based Dose Calculator

Dose per kg × Weight (kg) = Ordered dose

From the order or assignment. This tool does not supply or check it.

Pounds are converted with 2.2 lb = 1 kg.

Calculated in your browser. Values are not saved or sent anywhere.

Calculated ordered dose

Enter the dose per kg from the order and the patient's weight, then select Calculate.

Example: 10 mg/kg × 50 kg = 500 mg

Educational Use & Safety

Educational and calculation use only. Dosage Calcs performs mathematical calculations using the values you enter. It does not determine whether a medication, dose, route, frequency, concentration, or infusion rate is appropriate or safe for a patient. Always verify medication orders, calculations, product labeling, and applicable clinical or institutional policies before medication administration. When in doubt, consult an appropriate licensed healthcare professional or pharmacist.

Educational Use & Safety

Educational use: You supply the dose per kg from the order, assignment, or reference. This tool does not decide what dose per kg is appropriate or safe. Learn more.

What this calculates

Some orders are written as an amount of drug per kilogram of body weight, such as 10 mg/kg. Before you can prepare anything, you need the total dose for this particular patient. That total is the dose per kg multiplied by the weight in kilograms.

The result is the calculated ordered dose, a mass such as 500 mg. It is not yet a number of tablets or milliliters. To get that, you use the calculated dose as the "desired" value in a Desired ÷ Have problem.

Formula and inputs

Dose per kg × Weight (kg) = Ordered dose

  • Dose per kg — the amount per kilogram written in the order, in mg/kg, mcg/kg, or g/kg.
  • Weight — the patient's weight in kilograms. You can enter pounds and the tool converts them.
  • Ordered dose — the result, in the mass unit of the dose per kg (mg/kg gives mg, mcg/kg gives mcg).

The kilograms cancel: mg/kg × kg leaves mg. If your units do not cancel that way, something in the setup is wrong.

Converting pounds to kilograms

Nursing dosage-calculation courses commonly use 2.2 lb = 1 kg. To convert, divide pounds by 2.2. This site uses that same factor everywhere, including the unit converter, so answers match typical coursework.

110 lb ÷ 2.2 = 50 kg

When pounds do not divide evenly (for example, 100 lb ÷ 2.2 = 45.4545… kg), the calculator carries the exact, unrounded weight into the next step and rounds only the displayed numbers. Your course may tell you to round the weight first; if it does, follow that instruction, and expect small differences.

Worked examples

Example 1: weight already in kg

Order: 10 mg/kg. Weight: 50 kg.

10 mg/kg × 50 kg = 500 mg

Example 2: weight in pounds

Order: 10 mg/kg. Weight: 110 lb.

110 lb ÷ 2.2 = 50 kg

10 mg/kg × 50 kg = 500 mg

Example 3: a small decimal dose

Order: 0.5 mg/kg. Weight: 22 lb.

22 lb ÷ 2.2 = 10 kg

0.5 mg/kg × 10 kg = 5 mg

Example 4: micrograms

Order: 250 mcg/kg. Weight: 4 kg.

250 mcg/kg × 4 kg = 1,000 mcg

The answer stays in mcg because the order was in mcg/kg. 1,000 mcg equals 1 mg, but the tool does not switch units for you; convert only if your problem asks for it.

From calculated dose to amount

After you calculate the ordered dose, the calculator offers an optional second step. Enter the available dose and the quantity it comes in, and it runs the same Desired ÷ Have × Quantity method used by the Dosage Calculator.

500 mg ÷ 250 mg × 5 mL = 10 mL

Common mistakes

  • Multiplying by the weight in pounds instead of kilograms. This overstates the dose by 2.2 times.
  • Multiplying pounds by 2.2 instead of dividing. Kilograms are always the smaller number.
  • Treating a per-day order as a per-dose order, or the reverse. Read the order wording carefully.
  • Losing track of mcg versus mg. Keep the unit from the order until a conversion is needed.
  • Rounding the weight early when your course says not to, or not rounding when it says to.

Rounding

The calculator works with exact values. Results that end are shown exactly, with no trailing zeros. Results that repeat are shown with a ≈ sign and labeled approximate. How to round a real dose depends on the dose form, the measuring device, and your course or facility policy.

What this tool does not do

It does not know any medication, does not suggest a dose per kg, and does not compare your result against a recommended range. A result here only means the multiplication is correct for the numbers you entered.

FAQ

Does this tell me if a mg/kg dose is safe?

No. It only multiplies the values you enter. Whether a dose is appropriate is a clinical decision.

Why 2.2 and not 2.2046?

2.2 lb per kg is the equivalency commonly used in nursing dosage-calculation courses. Using one factor throughout keeps worked problems consistent.

Can I enter weight in grams?

Not in this calculator. Convert grams to kilograms first (1 kg = 1,000 g).

What about per-day doses divided into several doses?

This version calculates the total from the dose per kg. Dividing a daily total into doses is a separate step you can do by hand.

Sources

Formulas, units, and terminology were checked against these open references. Wording on this page is our own.

All sources · How we build and test calculators