Unit Converter: The Reference You Actually Need
Most unit conversion is lookup, not math. The formula for Fahrenheit to Celsius exists but nobody memorizes it — you look it up. Here's the reference for the conversions that come up most often, plus the ones that are genuinely confusing.
Temperature
The formulas everyone forgets:
- °F to °C: subtract 32, then multiply by 5/9
- °C to °F: multiply by 9/5, then add 32
The shortcuts worth memorizing:
- 0°C = 32°F (water freezes)
- 100°C = 212°F (water boils)
- 37°C = 98.6°F (body temperature)
- 20°C = 68°F (comfortable room)
Quick approximation: double the Celsius and add 30 for a rough Fahrenheit equivalent. (20°C → 70°F, off by 2. Good enough for weather.)
Cooking Conversions That Actually Matter
Volume:
- 3 teaspoons = 1 tablespoon
- 4 tablespoons = ¼ cup
- 16 tablespoons = 1 cup
- 2 cups = 1 pint
- 2 pints = 1 quart
- 4 quarts = 1 gallon
Weight:
- 1 ounce = 28.35 grams
- 1 pound = 453.6 grams
- 1 kilogram = 2.205 pounds
The one that causes constant recipe failures: 1 cup of flour ≠ 1 cup of butter in weight. Volume measurements are consistent; weight varies by ingredient density. Flour is ~125g/cup; butter is ~227g/cup; sugar is ~200g/cup. Use a kitchen scale for baking.
Speed
- 60 mph = 96.6 km/h (approximately 100 km/h)
- 100 km/h = 62.1 mph
- 1 knot = 1.15 mph = 1.85 km/h
Area
- 1 square foot = 0.093 square meters
- 1 acre = 43,560 square feet = 4,047 square meters
- 1 hectare = 2.47 acres = 10,000 square meters
The Metric Prefixes Worth Knowing
kilo (k) = 1,000 × | mega (M) = 1,000,000 × | giga (G) = 1,000,000,000 ×
milli (m) = 0.001 × | micro (μ) = 0.000001 × | nano (n) = 0.000000001 ×
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Frequently Asked Questions
Why does my recipe fail when I convert cup measurements to grams?
Volume and weight aren't interchangeable—1 cup of flour (125g) weighs completely different from 1 cup of butter (227g) because of ingredient density. For baking, always use a kitchen scale to measure by weight rather than volume cups, since small density differences compound quickly in recipes that require precision.
How do I quickly convert Celsius to Fahrenheit in my head?
Double the Celsius temperature and add 30 for a close approximation. For example, 20°C becomes 40 + 30 = 70°F (the actual answer is 68°F, off by just 2 degrees). This works well for weather estimates when you don't need perfect accuracy.
What's the difference between a knot, mph, and km/h?
A knot equals 1.15 mph or 1.85 km/h—it's used in aviation and maritime contexts. For reference, 60 mph is approximately 100 km/h, and 100 km/h equals about 62 mph. Understanding these ratios helps when comparing speeds across different measurement systems.
How many grams are in a tablespoon of flour?
Since flour measures ~125g per cup and there are 16 tablespoons in a cup, one tablespoon of flour weighs roughly 8 grams. However, this varies slightly depending on how packed the flour is, so a kitchen scale is still your most reliable option for baking.
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