Nursing Unit Conversions
Units must match before any dosage calculation. These are the conversions Dosage Calcs uses, and the reasoning that makes them easy to rebuild.
In this lesson
- The metric mass and volume relationships
- Why you multiply toward smaller units and divide toward larger ones
- Pounds to kilograms with 2.2
- Hours and minutes
What you're solving for
The same amount written in a different unit. A conversion never changes how much there is.
The conversions used on Dosage Calcs
| Type | Relationship |
|---|---|
| Mass | 1 g = 1,000 mg |
| Mass | 1 mg = 1,000 mcg |
| Mass | 1 g = 1,000,000 mcg |
| Volume | 1 L = 1,000 mL |
| Weight | 1 kg = 2.2 lb |
| Time | 1 hr = 60 min |
Larger and smaller units
Metric prefixes step by 1,000 for the units used here: g → mg → mcg. Moving to a smaller unit means you need more of them, so multiply. Moving to a larger unit means fewer, so divide. Asking “should the number get bigger or smaller?” catches most conversion errors.
g to mcg skips a step: 1,000 × 1,000 = 1,000,000. The same logic applies to L and mL (1,000). Dosage Calcs uses mcg for micrograms throughout the site for consistent medication-math notation.
Worked examples
Metric mass and volume
Convert each value.
- 0.5 g × 1,000 = 500 mg (1 g = 1,000 mg)
- 0.25 mg × 1,000 = 250 mcg (1 mg = 1,000 mcg)
- 750 mcg ÷ 1,000 = 0.75 mg (1 mg = 1,000 mcg)
- 1,500 mg ÷ 1,000 = 1.5 g (1 g = 1,000 mg)
- 0.002 g × 1,000,000 = 2,000 mcg (1 g = 1,000,000 mcg)
- 1.5 L × 1,000 = 1,500 mL (1 L = 1,000 mL)
Answer: 500 mg; 0.75 mg; 1,500 mL
Pounds to kilograms
A fictional patient weighs 154 lb. What is the weight in kg?
154 lb ÷ 2.2 = 70 kg
A kilogram is heavier than a pound, so the number of kilograms is smaller: divide by 2.2.
- 20 kg × 2.2 = 44 lb (1 kg = 2.2 lb)
Answer: 70 kg
Minutes and hours
Write 90 minutes in hours, and 2.5 hours in minutes.
- 90 min ÷ 60 = 1.5 hr (1 hr = 60 min)
- 2.5 hr × 60 = 150 min (1 hr = 60 min)
Answer: 1.5 hr; 150 min
Common mistakes
Using 1,000 for g ↔ mcg
- What goes wrong
- 0.002 g × 1,000 = 2 mcg
- Why it fails
- g to mcg is two metric steps.
- Correct approach
- 0.002 g × 1,000,000 = 2,000 mcg
Multiplying pounds by 2.2
- What goes wrong
- 154 lb × 2.2 = 338.8 kg
- Why it fails
- The kg number must be smaller than the lb number.
- Correct approach
- 154 lb ÷ 2.2 = 70 kg
Quick self-check
Convert 0.1 mg to mcg.
Show the answer
0.1 mg × 1,000 = 100 mcg
Check any conversion with the nursing unit converter, or keep the med-math quick reference handy.
Calculate and practice
Related lessons
- Dosage Calculation Basics — The parts of every dosage problem and how to set one up before you calculate.
- Dimensional Analysis for Dosage Calculations — Chain conversion factors so unwanted units cancel.
- Weight-Based Dosage Calculations — Multiply a given dose per kg by weight, converting pounds first.
Sources
- Nursing Skills — Math Calculations — Open RN / NCBI Bookshelf
- Pharmacology for Nurses — 2.4 Dosage Calculations — OpenStax
- Writing SI Metric System Units — NIST
Explanations are original Dosage Calcs wording. See all sources and the methodology.
Educational Use & Safety
Educational content only. These lessons teach medication math using fictional values and do not determine an appropriate medication, dose, infusion rate, or treatment for an actual patient.
Educational Use & Safety