Measurement, time & conversions · Topic 11 of 15

Household ↔ Metric Conversions

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Math · household ↔ metric

Memorize the rounded equivalents (tsp 5 mL, tbsp 15 mL, oz 30 mL, cup 240 mL, kg 2.2 lb), then convert by proportion.

01 · Fluids1 oz = 30 mL

02 · Spoon doses1 tsp = 5 mL

03 · Weight1 kg = 2.2 lb

lb → kg: divide by 2.2; kg → lb: multiply by 2.2

I&O: convert every item to mL, then total intake and output separately

1 teaspoon (tsp) = 5 mL must know

1 tablespoon (tbsp) = 3 tsp = 15 mL must know

1 fluid ounce (oz) = 30 mL must know

1 cup = 8 oz = 240 mL must know

1 kilogram (kg) = 2.2 pounds (lb) must know

1 inch (in) = 2.54 cm (exact; 63 in = 160.02 cm)

1 pint (pt) = 2 cups = 16 oz = 480 mL

1 quart (qt) = 2 pints = 32 oz ≈ 960 mL (about 1 L)

Write the equivalence as a fraction, wanted unit on top (30 mL/1 oz)

Multiply so the old unit cancels out

Check the size: smaller unit → bigger number

154 lb ÷ 2.2 = 70 kg

Worked examples

6 + 8 + 4 oz = 18 oz × 30 = 540 mL intake

Balance = intake − output: 1,800 − 1,350 = 450 mL

Commonly confused

	Household → metric	Metric → household
Volume (oz and mL)	oz × 30 (18 oz = 540 mL)	mL ÷ 30 (240 mL = 8 oz)
Weight (lb and kg)	lb ÷ 2.2 (154 lb = 70 kg)	kg × 2.2 (70 kg = 154 lb)
Length (in and cm)	in × 2.54 (63 in = 160.02 cm)	cm ÷ 2.54
The number gets…	Bigger for mL and cm, smaller for kg	Smaller for oz and in, bigger for lb

mL → oz: divide by 30 (240 mL = 8 oz, not 7,200)

Show 3 more facts

1 gallon (gal) = 4 quarts = 128 oz

Convert to one unit before adding (never add oz to mL)

Fluid ounce (30 mL) is volume; weight ounce ≈ 28 g (16 oz = 1 lb)

Pearl

Liquids by the numbers: 5, 15, 30, 240 — teaspoon, tablespoon, ounce, cup, all in mL.

Practice this topic, then test the whole section.

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