What is the difference between mcg and µg?

They are the same unit — microgram. 'mcg' is the preferred clinical abbreviation because 'µg' (with the Greek mu) can be misread as 'mg' (milligram) in handwritten notes, creating a 1,000-fold error risk. ISMP recommends writing 'mcg' always.

Why do some drug doses look different in Australian vs US references?

Most AU drug doses are in mg or mcg, while some older US references use grains or other imperial units. Always work in SI units (mg, mcg) for clinical calculations in Australia.

What temperature is considered fever in adults?

In Australia, fever is defined as a temperature ≥38.0°C (100.4°F). Temperatures ≥39.0°C are considered high fever and warrant more urgent assessment.

Unit Converter — Free Nurses Calculator

🎯

Drug chart says 0.5 g, you have mg on hand. Or the patient's temperature is in Fahrenheit and you need Celsius for documentation. You need the conversion before anything else.

Unit Converter

Converter

Conversion type

Value

× 1000: g→mg · mg→mcg · L→mL ÷ 1000: mg→g · mcg→mg · mL→L lb→kg: × 0.4536 · °C→°F: ×9/5+32 Normal body temp: 36.1–37.2°C (97–99°F)

Reference: NCBI Nursing Skills Ch.5 · NPS MedicineWise

⚕️ Clinical safety: 🇦🇺 Verify with facility drug formulary and senior clinician · Meets AHPRA/ACSQHC standards

1 What this calculator does

Converts between common clinical units: mass (mg, g, mcg), volume (mL, L), length (cm, m, inches), weight (kg, lb) and temperature (°C, °F). Covers the conversions that come up most often in medication rounds and clinical documentation.

2 Formula & professional reasoning

Mass: 1 g = 1,000 mg = 1,000,000 mcg  |  1 mg = 1,000 mcg
Weight: 1 kg = 2.2046 lb  |  1 lb = 0.4536 kg
Temp: °C = (°F − 32) × 5/9  |  °F = (°C × 9/5) + 32
Volume: 1 L = 1,000 mL

Clinical unit errors are a leading cause of medication harm. The three highest-risk conversions in nursing are: (1) g to mg (10× errors on drug doses), (2) lb to kg (weight-based dosing errors in patients who report weight in pounds), and (3) mcg to mg (1,000× errors on vasoactive drugs and electrolytes). Knowing the base relationships prevents calculator dependence for simple conversions.

3 Worked examples

⚠️ Illustrative example only — not clinical or professional instruction.

Basic

Grams to milligrams

Given: 0.5 g paracetamol ordered

Working: 0.5 × 1,000

Answer: 500 mg

💡 Stock is in mg — this is the value to enter into your dose calculation.

Standard

Pounds to kilograms for dosing

Given: Patient reports weight as 176 lb

Working: 176 ÷ 2.2046

Answer: 79.8 kg (rounds to 80 kg)

💡 Always use kg for weight-based medication calculations. Round to nearest 0.5 or 1 kg.

Advanced

Temperature Fahrenheit to Celsius

Given: Patient's US records show temperature 101.3 °F

Working: (101.3 − 32) × 5/9 = 69.3 × 0.556

Answer: 38.5 °C — low-grade fever

💡 Australian documentation is always in Celsius. 38.0°C is the standard fever threshold.

4 Sanity check

g → mg: multiply by 1,000

0.5 g = 500 mg · 1.5 g = 1,500 mg

The most common conversion error in drug calculations.

mcg → mg: divide by 1,000

500 mcg = 0.5 mg · 50 mcg = 0.05 mg

Digoxin, fentanyl, alfentanil: always in mcg — convert carefully.

lb → kg: divide by 2.2

154 lb ≈ 70 kg · 220 lb = 100 kg

Quick mental check: 2.2 lb per kg.

Normal body temp

36.1–37.2 °C · 97–99 °F

Fever: ≥38.0°C (100.4°F). Hypothermia: <35.0°C (95°F).

5 Common errors

Error	Cause	Consequence	Fix
Confusing mcg and mg	Decimal point placement or abbreviation misread	1,000× dosing error — potentially fatal for vasoactive drugs	Write 'mcg' never 'µg' in clinical notes. Double-check every conversion between mcg and mg.
Using 2.2 to convert kg to lb (wrong direction)	Multiplying instead of dividing	Patient appears to weigh 2.2× their actual weight	To get kg from lb: divide by 2.2. To get lb from kg: multiply by 2.2.
Rounding intermediate conversions	Converting and rounding before using in a further calculation	Compounding rounding error	Complete all conversions first, then round only at the final answer
Using Fahrenheit thresholds in a Celsius environment	Working from US reference materials	Fever or hypothermia missed	AU/UK/NZ use Celsius exclusively. Fever threshold is 38.0°C (not 100.4°F)