CWC Ch. 6: Converting Within and Between Systems

Approximate equivalents between SI and household

1 tsp = 5 mL

1 tbsp = 15 mL

1 oz = 30 mL

1 cup = 8 oz = 240 mL

16 oz = 1 lb, 2.2 lb = 1 kg

1 in = 2.5 cm

Conversion factor

a ratio of equivalent measurements; ex. 1000 mg = 1 g

Ratio and proportion

1. State conversion factor

2. Add incomplete ratio on the other sign of the = with units in same sequence; ex. mg : g = mg : g

3. Label all terms in the proportion (but do not carry when multiplying or dividing)

4. Solve the problem; the product of the means = the product of the extremes

5. Label the final answer for x with appropriate unit

Dimensional analysis

1. Identify the desired unit

2. Write the conversion factor in fraction format so that the desired unit is in the NUMERATOR

3. Write the unit in the next numerator to match the previous denominator unit

4. Cancel the alternate denominator/numerator units to leave the unit desired

5. Perform the mathematical process indicated

Conversion factor method

1. State conversion factor

2. State which unit is larger

3. Multiply known value by desired unit value (larger to smaller) or divide (smaller to larger)

ex. 4 oz = x mL

Conversion factor: 1 oz = 30 mL

1 oz > 1 mL

4 x 30

= 120 mL

Hourly urine output for an adult to maintain proper renal function

30 mL/h to 50 mL/h