Conversions · Published by Maksym Shevchuk · Updated
Nursing dosage conversion chart: metric and household equivalents
Short answer
Nursing dosage calculations mostly use 1 g = 1,000 mg, 1 mg = 1,000 mcg, 1 kg = 2.2 lb, 1 L = 1,000 mL and 1 hr = 60 min, plus the household measures 1 tsp = 5 mL, 1 tbsp = 15 mL and 1 fl oz = 30 mL. Write each as a factor with the unit you leave on the bottom.
The chart
Every factor below is one DoseReady's own problems use; the metric and household equivalents match the ones Open RN lists for nursing calculations. Read a row left to right: to go from the first unit to the second, multiply by the factor in the last column.
| From | To | Equivalent | Multiply by |
|---|---|---|---|
| Grams (g) | Milligrams (mg) | 1 g = 1,000 mg | 1,000 mg / 1 g |
| Milligrams (mg) | Grams (g) | 1 g = 1,000 mg | 1 g / 1,000 mg |
| Milligrams (mg) | Micrograms (mcg) | 1 mg = 1,000 mcg | 1,000 mcg / 1 mg |
| Micrograms (mcg) | Milligrams (mg) | 1 mg = 1,000 mcg | 1 mg / 1,000 mcg |
| Kilograms (kg) | Grams (g) | 1 kg = 1,000 g | 1,000 g / 1 kg |
| Grams (g) | Kilograms (kg) | 1 kg = 1,000 g | 1 kg / 1,000 g |
| Pounds (lb) | Kilograms (kg) | 1 kg = 2.2 lb | 1 kg / 2.2 lb |
| Kilograms (kg) | Pounds (lb) | 1 kg = 2.2 lb | 2.2 lb / 1 kg |
| Liters (L) | Milliliters (mL) | 1 L = 1,000 mL | 1,000 mL / 1 L |
| Milliliters (mL) | Liters (L) | 1 L = 1,000 mL | 1 L / 1,000 mL |
| Teaspoons (tsp) | Milliliters (mL) | 1 tsp = 5 mL | 5 mL / 1 tsp |
| Tablespoons (tbsp) | Milliliters (mL) | 1 tbsp = 15 mL | 15 mL / 1 tbsp |
| Fluid ounces (fl oz) | Milliliters (mL) | 1 fl oz = 30 mL | 30 mL / 1 fl oz |
| Milliliters (mL) | Fluid ounces (fl oz) | 1 fl oz = 30 mL | 1 fl oz / 30 mL |
| Hours (hr) | Minutes (min) | 1 hr = 60 min | 60 min / 1 hr |
| Minutes (min) | Hours (hr) | 1 hr = 60 min | 1 hr / 60 min |
How to use a conversion factor
Write the amount you have, then multiply it by the factor whose bottom unit is the unit you are leaving. That unit cancels, and the one left over is the unit you want. If a unit does not cancel, the factor is upside down.
Check the size of the answer as well. Going to a smaller unit, such as grams to milligrams, gives a bigger number; going to a larger unit gives a smaller one. The worked example in this guide turns a dose in milligrams into micrograms that way.
An order for digoxin is written as 0.25 mg daily. The tablets on hand are labeled in micrograms. Express the ordered dose in micrograms.
Dimensional analysis
0.25 × 1,000 ÷ 1 = 250
Ratio and proportion
1 mg is to 1,000 mcg as 0.25 mg is to x mcg
0.25 × 1,000 ÷ 1 = 250
x = 250 mcg
Formula method
The formula method (D ÷ H × Q) does not fit this problem. The chain above is the working.
The answer
The answer under the stated rule
250 mcg
Nearest tenth, half rounds up. The working comes to 250 mcg exactly, so the rule leaves it as it is.
What each slip gives here
- Decimal point one place out2,500 mcg or 25 mcg
- Conversion skipped0.3 mcg
What this problem is built from
Household measures
Open RN lists the household equivalents nursing calculations use: 1 tsp = 5 mL, 1 tbsp = 3 tsp = 15 mL, and 1 oz = 30 mL. A label strength in milligrams per 5 mL often pairs with an order or a measuring spoon in teaspoons, so the teaspoon factor comes up in oral liquid problems.
The second worked example in this guide turns a feed in milliliters into fluid ounces.
An infant takes 150 mL of formula at a feeding. The intake record is kept in milliliters, and the parents measure feeds at home with a bottle marked in fluid ounces. Express the volume taken in fluid ounces.
Dimensional analysis
150 × 1 ÷ 30 = 5
Ratio and proportion
30 mL is to 1 fl oz as 150 mL is to x fl oz
150 × 1 ÷ 30 = 5
x = 5 fl oz
Formula method
The formula method (D ÷ H × Q) does not fit this problem. The chain above is the working.
The answer
The answer under the stated rule
5 fl oz
Nearest tenth, half rounds up. The working comes to 5 fl oz exactly, so the rule leaves it as it is.
What each slip gives here
- Decimal point one place out50 fl oz or 0.5 fl oz
- Conversion factor inverted4,500 fl oz
- Conversion skipped150 fl oz
What this problem is built from
Pounds and kilograms
Weight-based orders are written per kilogram, so a weight given in pounds is converted first, with 1 kg over 2.2 lb. NCC MERP recommends that patients be weighed, and their weights documented, in metric units; a problem that gives pounds asks you to make that conversion yourself.
Some programs round the weight to the tenth before using it, and some do not round until the final answer; the rounding rules guide compares them. More are on the weight-based dosing practice page.
The inverted factor
Set a factor upside down and the units do not cancel, and the answer is off by the factor squared: between grams and milligrams, a millionfold. Writing the units in every step shows the mistake before the arithmetic does. The guide to common mistakes shows the wrong answer this slip leaves.
Drop factors are not in the chart
Drops per milliliter depend on the tubing set, so the drop factor in a problem comes from the problem or the tubing package. Open RN's table lists the common ones, 10, 12, 15 or 20 drops per milliliter and 60 for microdrip tubing, and the IV drip rate guide turns each into drops per minute.
Print it
Your browser's Print command prints this page on its own, without the site's menus. Practice the conversions on the unit conversion practice page, where each problem opens to its worked solution.
Practice this
Unit conversion practice problems for nursing students
Each problem opens to its worked solution, the answer under a stated rounding rule and the sources it is built from.
Questions
- How many milligrams are in a gram?
- There are 1,000 milligrams in 1 gram. To turn grams into milligrams, multiply by 1,000 mg over 1 g; to turn milligrams into grams, multiply by 1 g over 1,000 mg.
- How many micrograms are in a milligram?
- There are 1,000 micrograms in 1 milligram, so a dose in milligrams is multiplied by 1,000 to give micrograms, and a dose in micrograms is divided by 1,000 to give milligrams.
- What pounds-to-kilograms factor do nursing dosage calculations use?
- Nursing dosage calculations use 1 kg = 2.2 lb: divide a weight in pounds by 2.2 to get kilograms. Some programs round that weight to the tenth before using it, so check your syllabus.
- How many milliliters are in a teaspoon and a tablespoon?
- Nursing calculations use 1 teaspoon = 5 mL and 1 tablespoon = 15 mL, the household equivalents Open RN lists, along with 1 fluid ounce = 30 mL.
Sources
- [1]Open RN, Nursing Skills 2e, 5.4 Equivalencies (WisTech Open, 2023)wtcs.pressbooks.pub
- [2]Open RN, Nursing Skills 2e, 5.6 Using Dimensional Analysis (WisTech Open, 2023)wtcs.pressbooks.pub
- [3]NCC MERP, Recommendations to Weigh Patients and Document Metric Weights (2018)nccmerp.org
No licensed clinician has reviewed this guide. How the guides are made. Exam practice, never for patient care. Follow your program's rules.
More guides
- The dosage calculation exam in nursing school: what is on it and how to prepare
- Dosage calculation exam rules by nursing program: passing scores, retakes and calculators
- Dosage calculation formulas for nursing: one table for the common problems
- Rounding rules for dosage calculations
- Leading and trailing zeros in medication doses: the ISMP rules for nursing
- Desired over have formula: how D/H × Q works in dosage calculations
- Ratio and proportion dosage calculations: how to set them up
- How to calculate mL/hr for an IV infusion
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- Reconstitution dosage calculation: from a powder vial to milliliters
- Weight-based dosage calculation: mg/kg doses from a weight in pounds
- Six dosage calculation mistakes and the wrong answers they leave
- Dimensional analysis for nursing dosage calculations
- IV drip rate formula: how to work out drops per minute