In short
Quick conversions for weather, fever, distance, weight, height, gas, cooking cups, oven heat, dates and the 12-hour clock.
The US uses its own units for almost everything: weather, speed, food and body weight. You do not need exact math. Learn a few anchor numbers.
Temperature (Fahrenheit, °F)
32°F = 0°C: water freezes. Expect ice on roads.
50°F = 10°C: cool. Wear a jacket.
68°F = 20°C: comfortable room temperature.
100°F = about 38°C: very hot.
Quick math: subtract 30, then divide by 2. 70°F is about 20°C.
Body temperature: 98.6°F (37°C) is normal. 100.4°F (38°C) or higher is a fever.
1 inch = 2.54 cm. 1 foot (12 inches) = about 30 cm. 1 yard (3 feet) = about 0.9 m.
1 mile = about 1.6 km. 5 miles = about 8 km.
Speed limits are in mph (miles per hour). 25 mph is about 40 km/h, 55 mph about 90 km/h, 70 mph about 113 km/h.
US forms and doctors ask for height in feet and inches and weight in pounds.
5 ft 0 in = 152 cm. 5 ft 6 in = 168 cm. 6 ft 0 in = 183 cm. It is written 5'6".
1 pound (lb) = about 0.45 kg. 1 kg = 2.2 lb. 60 kg = about 132 lb; 80 kg = about 176 lb.
1 ounce (oz) = about 28 g. 1 lb = 16 oz.
Fluid ounce (fl oz) measures liquid: about 30 ml. A 12 fl oz can is about 355 ml.
1 gallon = about 3.8 liters. Gas and milk are sold by the gallon. Half a gallon is about 1.9 liters.
US recipes use cups and spoons, measured by volume, not weight.
1 cup = about 240 ml. 1 tablespoon (tbsp) = about 15 ml. 1 teaspoon (tsp) = about 5 ml.
1 stick of butter = half a cup, about 113 g.
Oven temperatures are in °F: 325°F = about 160°C, 350°F = about 175°C, 375°F = about 190°C, 400°F = about 200°C, 425°F = about 220°C, 450°F = about 230°C.
A set of measuring cups and spoons is cheap at any grocery store.
Dates are written month first: 03/04/2027 means March 4, not April 3. Forms show MM/DD/YYYY.
The 12-hour clock: AM is midnight to noon, PM is noon to midnight. 12:00 PM is noon. 7:00 PM is 19:00.
Room and home sizes are in square feet. 100 sq ft = about 9.3 square meters; a 700 sq ft apartment is about 65 square meters.
Clothing and shoe sizes are different too. See Clothing and shoe sizes, and dressing for the weather.
Writing your birth date day-first on a form.
Setting the oven to 180 because the recipe at home said 180°C. In °F, that barely warms the food.
Reading a weather forecast of "40" as warm. 40°F is about 4°C.