Quick Reference
Metric ↔ Imperial
Key anchor equivalences to keep in your head, with handy mnemonics and tips.
Length & Distance
| Measure | Equals | Precision | Tip |
|---|---|---|---|
| 1 inch | 2.54 cm | Exact | An inch is about the width of your thumb. |
| 1 foot | 30.48 cm | Exact | A foot is almost exactly 30 cm. |
| 1 yard | 0.9144 m | Exact | A metre is a yard and a bit (about 10% more). |
| 1 mile | 1.609 km | Exact | Multiply miles by 1.6 for a quick km estimate. |
| 1 cm | 0.3937 in | Exact | Roughly 2.5 cm per inch. |
| 1 km | 0.6214 mi | Approx | 5 miles ≈ 8 km (the Fibonacci trick). |
Weight & Mass
| Measure | Equals | Precision | Tip |
|---|---|---|---|
| 1 oz (avdp) | 28.35 g | Exact | About the weight of a slice of bread. |
| 1 pound | 453.6 g | Exact | A kilogram is about 2.2 pounds. |
| 1 stone | 6.35 kg | Exact | Used in the UK for body weight: 14 lb = 1 stone. |
| 1 kg | 2.205 lb | Approx | A bag of sugar is typically 1 kg (2.2 lb). |
| 1 troy oz | 31.10 g | Exact | For gold/silver — heavier than a regular oz. |
Volume (Liquid)
| Measure | Equals | Precision | Tip |
|---|---|---|---|
| 1 US fl oz | 29.57 mL | Exact | About 2 tablespoons. |
| 1 US cup | 236.6 mL | Exact | Just under a quarter litre. |
| 1 US pint | 473.2 mL | Exact | A US pint is smaller than an Imperial pint. |
| 1 US gallon | 3.785 L | Exact | About 4 litres (Imperial gallon is 4.55 L). |
| 1 litre | 33.81 US fl oz | Approx | A litre is close to a quart (just 5% more). |
| 1 Imp pint | 568.3 mL | Exact | A proper British pint — 20% bigger than US. |
Area
| Measure | Equals | Precision | Tip |
|---|---|---|---|
| 1 sq ft | 929 cm² | Approx | About the area of a large floor tile. |
| 1 acre | 4,047 m² | Exact | About 75% of a football field. |
| 1 sq mi | 2.59 km² | Approx | 1 sq mi = 640 acres. |
| 1 hectare | 2.471 acres | Approx | About 2.5 acres, or 100m × 100m. |
Temperature Landmarks
| Fahrenheit | Celsius | Significance | |
|---|---|---|---|
| 32°F | = | 0°C | Freezing point of water |
| 72°F | = | 22.2°C | Comfortable room temperature |
| 98.6°F | = | 37°C | Normal body temperature |
| 212°F | = | 100°C | Boiling point of water |
| 350°F | = | 176.7°C | Common baking temperature |
| −40°F | = | −40°C | Where both scales meet! |
Quick Formulas
°F → °C
°C = (°F − 32) × 5/9
°C → °F
°F = °C × 9/5 + 32
Miles → Km
km = miles × 1.60934
Kg → Lb
lb = kg × 2.20462