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Pocket reference · v2

US to metric,
in your head.

Mental shortcuts within ~5% accuracy. Good enough for shopping, driving, and the weather forecast.

01

Temperature

°C → °F
double + 30
20°C → 40 + 30 = 70°F · actual 68
30°C → 60 + 30 = 90°F · actual 86
°F → °C
−30, then halve
90°F → 60 / 2 = 30°C · actual 32
50°F → 20 / 2 = 10°C · exact
Anchor°F°C
Freezing320
Cool day5010
Room temp6820
ATL summer8630
Body temp98.637
Boiling212100
Drift
The doubling rule slips at extremes. Above 30°C or below −10°C, expect ±2°C error.
02

Distance & Speed

Miles → km · the Fibonacci trick
Each mile value maps to the next number in the sequence as km.
3mi→5km
5mi→8km
8mi→13km
13mi→21km
21mi→34km
34mi→55km
55mi→89km
Miles → km · general
× 1.6
60 mi → 96 km
100 mi → 160 km
mph → km/h
× 1.6
70 mph (interstate) → 112 km/h
Feet → meters
÷ 3 (roughly)
6 ft → 1.8 m
10 ft → 3 m
Inches → cm
× 2.5
12 in → 30 cm
32 in waist → 81 cm
Yards → meters
subtract 10%
100 yd → 90 m
03

Weight

Pounds → kg
halve, then −10%
150 lb → 75 → 67.5 kg · actual 68
200 lb → 100 → 90 kg · actual 91
kg → pounds
double, then +10%
80 kg → 160 → 176 lb · exact
Ounces → grams
× 30
8 oz steak → 240 g · actual 227
Trap
US short ton = 907 kg, not 1000 kg. A metric tonne is ~10% heavier. Matters for freight.
04

Volume

Fluid oz → ml
× 30
12 fl oz can → 355 ml
16 fl oz pint → 470 ml
Gallons → liters
× 4, then −5%
10 gal → 40 → 38 L
USMetricMemo
1 tsp5 ml—
1 tbsp15 ml3 tsp
1 cup240 ml¼ L
1 pint470 ml½ L
1 quart950 ml1 L
1 gallon3.8 L4 qt
Trap
US gallon ≠ UK gallon. UK = 4.55 L (20% bigger). Old UK car specs will mislead you.
05

Oven & Cooking

Use°F°C
Slow / braise275140
Cake325165
Default bake350175
Cookies375190
Roast veg400200
Pizza / sear425220
High roast450230
Butter stick
1 stick = 113 g
= ½ cup = 8 tbsp

Practice Mode

Test your mental math skills!