Household Measurements¶
Overview¶
While the metric system is standard in clinical settings, nurses frequently encounter household measurements when:
- Taking medication histories from patients
- Instructing patients on home medication administration
- Working with liquid medications measured by spoon or cup
Understanding how household units relate to metric units is essential for patient education and safe home care instructions.
Common Household Units¶
Volume¶
| Household Unit | Abbreviation | Metric Equivalent |
|---|---|---|
| teaspoon | tsp | 5 mL |
| tablespoon | tbsp | 15 mL |
| fluid ounce | fl oz | 30 mL |
| cup | c | 240 mL |
| pint | pt | 480 mL |
| quart | qt | 960 mL |
Weight¶
| Household Unit | Abbreviation | Metric Equivalent |
|---|---|---|
| ounce | oz | 30 g |
| pound | lb | 453.6 g |
| pound | lb | 0.454 kg |
Key Weight Conversion¶
This is the most important household-to-metric weight conversion in nursing — used constantly for weight-based dosing.
Memorization Tips¶
Volume Relationships
Build up from the teaspoon:
[1 \text{ tbsp} = 3 \text{ tsp} = 15 \text{ mL}] [1 \text{ fl oz} = 2 \text{ tbsp} = 30 \text{ mL}] [1 \text{ cup} = 8 \text{ fl oz} = 240 \mL}]
Weight Shortcut
To convert lb to kg — divide by 2.2
To convert kg to lb — multiply by 2.2
Clinical Application¶
Example 1: A patient reports taking 2 teaspoons of liquid medication at home. Convert to mL for the medication record:
Example 2: A patient weighs 154 lb. A weight-based medication requires the weight in kg. Convert:
Example 3: A discharge instruction says to take 1 tablespoon of medication twice daily. How many mL per day?
Example 4: A patient is prescribed 30 mL of an oral solution. How many tablespoons should you instruct them to take at home?
Patient Education¶
Spoon Sizes Vary
Household spoons are not standardized. A kitchen teaspoon may hold anywhere from 3 to 7 mL. Always instruct patients to use a calibrated measuring device — oral syringe, medicine cup, or dosing spoon — rather than a kitchen spoon.
Documenting Intake
In clinical settings, fluid intake is always documented in mL, never in household units. Convert any household measurements before recording.
Practice Problems¶
Problem 1
A patient takes 3 teaspoons of cough syrup. Convert to mL.
Answer
Problem 2
Convert 88 lb to kg.
Answer
Problem 3
A patient needs to take 45 mL of an oral solution at home. How many tablespoons is that?
Answer
Problem 4
Convert 60 kg to lb.
Answer
Problem 5
A child weighs 44 lb. A weight-based antibiotic is ordered at 10 mg/kg. What is the child's weight in kg and what is the dose?
Answer
Step 1 — Convert weight: [44 \text{ lb} \div 2.2 = 20 \text{ kg}]
Step 2 — Calculate dose: [10 \text{ mg/kg} \times 20 \text{ kg} = 200 \text{ mg}]
Clinical Tip
Always obtain and document patient weight in kg in clinical settings. If a patient only knows their weight in pounds, convert immediately and record in kg to avoid confusion during weight-based dosing calculations.