Unit Conversions Reference
The Observatory Almanac — Section 15.1
Length
Imperial / US Customary Relationships
| Unit |
Equivalent |
| 1 inch (in) |
12 inches = 1 foot |
| 1 foot (ft) |
3 feet = 1 yard |
| 1 yard (yd) |
1,760 yards = 1 mile |
| 1 mile (mi) |
5,280 feet = 1,760 yards |
Imperial ↔ Metric
| Imperial |
Metric |
Metric |
Imperial |
| 1 inch |
25.4 mm |
1 mm |
0.0394 in |
| 1 inch |
2.54 cm |
1 cm |
0.394 in |
| 1 foot |
30.48 cm |
1 m |
3.281 ft |
| 1 foot |
0.3048 m |
1 m |
1.094 yd |
| 1 yard |
0.9144 m |
1 km |
0.621 mi |
| 1 mile |
1.609 km |
1 km |
3,281 ft |
| 1 mile |
1,609 m |
|
|
Quick Reference — Inches to Centimeters
| Inches |
cm |
Inches |
cm |
| 1" |
2.5 |
12" (1 ft) |
30.5 |
| 2" |
5.1 |
18" |
45.7 |
| 3" |
7.6 |
24" (2 ft) |
61.0 |
| 4" |
10.2 |
36" (3 ft / 1 yd) |
91.4 |
| 5" |
12.7 |
48" (4 ft) |
121.9 |
| 6" |
15.2 |
60" (5 ft) |
152.4 |
| 9" |
22.9 |
72" (6 ft) |
182.9 |
Quick Reference — Miles to Kilometers
| Miles |
km |
km |
Miles |
| 1 |
1.6 |
1 |
0.6 |
| 5 |
8.0 |
5 |
3.1 |
| 10 |
16.1 |
10 |
6.2 |
| 25 |
40.2 |
25 |
15.5 |
| 50 |
80.5 |
50 |
31.1 |
| 100 |
160.9 |
100 |
62.1 |
| 500 |
804.7 |
500 |
310.7 |
Nautical Miles
|
|
| 1 nautical mile (nmi) |
1.852 km |
| 1 nautical mile |
1.151 mi |
| 1 nautical mile |
6,076 feet |
| 1 mile |
0.869 nmi |
| 1 km |
0.540 nmi |
Weight / Mass
Imperial / US Relationships
|
|
| 16 ounces (oz) |
= 1 pound (lb) |
| 2,000 pounds |
= 1 short ton (US) |
| 2,240 pounds |
= 1 long ton (UK) |
| 14 pounds |
= 1 stone (UK) |
Imperial ↔ Metric
| Imperial |
Metric |
Metric |
Imperial |
| 1 oz |
28.35 g |
1 g |
0.035 oz |
| 1 lb |
453.6 g |
100 g |
3.527 oz |
| 1 lb |
0.454 kg |
1 kg |
2.205 lb |
| 1 short ton |
907.2 kg |
1 tonne (metric) |
2,205 lb |
| 1 long ton |
1,016 kg |
1 tonne |
1.102 short tons |
| 1 stone |
6.350 kg |
1 kg |
0.157 stone |
Quick Reference — Pounds to Kilograms
| lb |
kg |
kg |
lb |
| 1 |
0.45 |
1 |
2.2 |
| 5 |
2.3 |
5 |
11.0 |
| 10 |
4.5 |
10 |
22.0 |
| 20 |
9.1 |
20 |
44.1 |
| 50 |
22.7 |
50 |
110.2 |
| 100 |
45.4 |
100 |
220.5 |
| 150 |
68.0 |
150 |
330.7 |
| 200 |
90.7 |
200 |
440.9 |
Stones (UK Body Weight)
| Stone |
Pounds |
kg |
| 8 st |
112 lb |
50.8 kg |
| 10 st |
140 lb |
63.5 kg |
| 11 st |
154 lb |
69.9 kg |
| 12 st |
168 lb |
76.2 kg |
| 13 st |
182 lb |
82.6 kg |
| 14 st |
196 lb |
88.9 kg |
| 15 st |
210 lb |
95.3 kg |
| 16 st |
224 lb |
101.6 kg |
Volume
US Liquid Volume Relationships
|
|
| 3 teaspoons (tsp) |
= 1 tablespoon (tbsp) |
| 2 tablespoons |
= 1 fluid ounce (fl oz US) |
| 8 fluid ounces |
= 1 cup |
| 2 cups |
= 1 pint (US) |
| 2 pints |
= 1 quart (US) |
| 4 quarts |
= 1 gallon (US) |
| 1 gallon (US) |
= 128 fl oz = 16 cups |
UK Fluid Measurements
|
|
| 1 UK fluid ounce |
= 28.41 ml (vs US fl oz = 29.57 ml) |
| 1 UK pint |
= 20 fl oz = 568 ml |
| 1 US pint |
= 16 fl oz = 473 ml |
| 1 UK gallon |
= 8 pints = 4.546 L |
| 1 US gallon |
= 8 US pints = 3.785 L |
Volume ↔ Metric
| US |
Metric |
| 1 teaspoon |
4.93 ml |
| 1 tablespoon |
14.79 ml |
| 1 US fl oz |
29.57 ml |
| 1 UK fl oz |
28.41 ml |
| 1 cup (US) |
236.6 ml |
| 1 US pint |
473.2 ml |
| 1 UK pint |
568.3 ml |
| 1 US quart |
946.4 ml (0.946 L) |
| 1 US gallon |
3,785 ml (3.785 L) |
| 1 UK gallon |
4,546 ml (4.546 L) |
Metric → US
| Metric |
US |
| 1 ml |
0.034 US fl oz |
| 100 ml |
3.38 US fl oz |
| 250 ml |
1.057 US cups |
| 500 ml |
2.113 US cups |
| 1 L |
1.057 US quarts |
| 1 L |
0.264 US gallons |
| 2 L |
0.528 US gallons |
Temperature
| Convert |
Formula |
| Fahrenheit → Celsius |
°C = (°F − 32) × 5/9 |
| Celsius → Fahrenheit |
°F = (°C × 9/5) + 32 |
| Celsius → Kelvin |
K = °C + 273.15 |
| Kelvin → Celsius |
°C = K − 273.15 |
| Fahrenheit → Kelvin |
K = (°F + 459.67) × 5/9 |
Quick Reference Chart
| °F |
°C |
Description |
| -40 |
-40 |
Equal point (-40°F = -40°C) |
| 0 |
-17.8 |
Very cold winter day |
| 14 |
-10 |
Severe cold |
| 32 |
0 |
Water freezes |
| 50 |
10 |
Cool day |
| 59 |
15 |
Mild |
| 68 |
20 |
Room temperature (cool) |
| 72 |
22.2 |
Comfortable room temp |
| 77 |
25 |
Warm |
| 86 |
30 |
Hot day |
| 95 |
35 |
Very hot |
| 100 |
37.8 |
Just above body temp |
| 98.6 |
37 |
Normal body temperature |
| 100.4 |
38 |
Low-grade fever |
| 104 |
40 |
High fever |
| 212 |
100 |
Water boils (sea level) |
| 350 |
177 |
Oven (moderate) |
| 375 |
191 |
Oven (moderate-hot) |
| 400 |
204 |
Oven (hot) |
| 425 |
218 |
Oven (very hot) |
| 450 |
232 |
Oven (extremely hot) |
Key Kelvin Reference Points
| K |
°C |
Description |
| 0 |
-273.15 |
Absolute zero |
| 273.15 |
0 |
Water freezes |
| 293 |
~20 |
Room temperature |
| 373.15 |
100 |
Water boils |
| 310 |
~37 |
Human body temperature |
Area
| Imperial |
Metric |
| 1 sq inch (in²) |
6.452 cm² |
| 1 sq foot (ft²) |
929.0 cm² = 0.0929 m² |
| 1 sq yard (yd²) |
0.836 m² |
| 1 acre |
4,047 m² = 0.405 hectare |
| 1 acre |
43,560 ft² |
| 1 sq mile |
2.590 km² = 259 hectares |
| 1 sq mile |
640 acres |
| Metric |
Imperial |
| 1 cm² |
0.155 in² |
| 1 m² |
10.764 ft² = 1.196 yd² |
| 1 hectare |
2.471 acres |
| 1 km² |
0.386 sq miles = 247.1 acres |
Quick Area Reference
| Acres |
Hectares |
Description (approx) |
| 0.5 |
0.2 |
Half acre |
| 1 |
0.4 |
Standard lot (US residential) |
| 5 |
2.0 |
Small homestead |
| 10 |
4.0 |
Small farm |
| 100 |
40.5 |
Large farm |
| 640 |
259 |
1 square mile |
Speed
| mph |
km/h |
Knots |
| 1 |
1.609 |
0.869 |
| 5 |
8.0 |
4.3 |
| 10 |
16.1 |
8.7 |
| 25 |
40.2 |
21.7 |
| 30 |
48.3 |
26.1 |
| 35 |
56.3 |
30.4 |
| 40 |
64.4 |
34.8 |
| 45 |
72.4 |
39.1 |
| 50 |
80.5 |
43.5 |
| 55 |
88.5 |
47.8 |
| 60 |
96.6 |
52.1 |
| 65 |
104.6 |
56.5 |
| 70 |
112.7 |
60.9 |
| 75 |
120.7 |
65.2 |
| 80 |
128.7 |
69.5 |
| 100 |
160.9 |
86.9 |
| 120 |
193.1 |
104.3 |
- mph → km/h: multiply by 1.609
- km/h → mph: multiply by 0.621
- mph → knots: multiply by 0.869
- knots → mph: multiply by 1.151
- knots → km/h: multiply by 1.852
Pressure
| Unit |
Equivalent |
| 1 atmosphere (atm) |
14.696 psi |
| 1 atm |
1.01325 bar |
| 1 atm |
101,325 Pa |
| 1 atm |
760 mmHg (Torr) |
| 1 bar |
14.504 psi |
| 1 bar |
0.9869 atm |
| 1 bar |
750.1 mmHg |
| 1 psi |
0.0689 bar |
| 1 psi |
0.068 atm |
| 1 psi |
51.71 mmHg |
| 1 mmHg |
0.0193 psi |
| 1 mmHg |
0.001316 atm |
| 1 mmHg |
133.3 Pa |
Common Pressure Reference Points
| Pressure |
psi |
bar |
Description |
| 0 |
0 |
0 |
Vacuum |
| Sea level air |
14.696 |
1.01 |
Standard atmosphere |
| Car tire |
30–35 |
2.07–2.41 |
Typical inflation |
| Road bike tire |
80–130 |
5.5–9.0 |
High pressure |
| Blood pressure systolic (normal) |
~1.74 |
~0.12 |
120 mmHg |
Energy
| Unit |
Equivalent |
| 1 calorie (cal, small) |
4.184 joules (J) |
| 1 Calorie (kcal, food) |
4,184 J = 4.184 kJ |
| 1 kilowatt-hour (kWh) |
3,600,000 J = 3.6 MJ |
| 1 kWh |
860 kcal (food Calories) |
| 1 BTU (British thermal unit) |
1,055.06 J |
| 1 BTU |
0.252 kcal |
| 1 BTU |
0.000293 kWh |
| 1 kcal |
3.968 BTU |
| 1 kcal |
0.001163 kWh |
| 1 kWh |
3,412 BTU |
Food Energy Quick Reference
| Food Calories (kcal) |
Joules |
BTU |
| 100 |
418,400 |
397 |
| 500 |
2,092,000 |
1,984 |
| 1,000 |
4,184,000 |
3,968 |
| 2,000 |
8,368,000 |
7,936 |
| 2,500 |
10,460,000 |
9,920 |
Cooking-Specific Conversions
Butter
| US Measurement |
Equivalent |
| 1 stick of butter |
1/2 cup = 8 tablespoons = 113g = 4 oz |
| 2 sticks |
1 cup = 227g = 8 oz |
| 4 sticks |
1 pound = 454g |
| 1/4 stick |
2 tablespoons = 28g |
Egg Substitutes (Per 1 Large Egg)
| Substitute |
Amount |
| Flax "egg" |
1 tbsp ground flax + 3 tbsp water (let sit 5 min) |
| Chia "egg" |
1 tbsp chia seeds + 3 tbsp water (let sit 5 min) |
| Applesauce |
1/4 cup (60ml) |
| Banana (mashed) |
1/4 cup (60ml) |
| Silken tofu |
1/4 cup (60ml), blended smooth |
| Aquafaba |
3 tbsp (chickpea liquid) |
| Commercial replacer |
Follow package (typically 1 tsp powder + 2 tbsp water) |
| Buttermilk |
1/4 cup (adds leavening) |
| Yogurt |
1/4 cup (adds moisture and binding) |
Best for baking cookies/cakes: flax egg or banana. Best for binding: silken tofu. Best for meringues: aquafaba.
Flour Conversions (1 Cup US)
| Flour Type |
Grams |
oz |
| All-purpose (spooned & leveled) |
120–125 g |
4.25 oz |
| All-purpose (scooped/packed) |
140–160 g |
5–5.5 oz |
| Bread flour |
120–130 g |
4.3 oz |
| Cake flour |
100 g |
3.5 oz |
| Whole wheat flour |
120 g |
4.25 oz |
| Almond flour |
96 g |
3.4 oz |
| Oat flour |
90–100 g |
3.2 oz |
| Cornstarch |
120 g |
4.25 oz |
| Rice flour |
160 g |
5.6 oz |
| Rye flour |
102 g |
3.6 oz |
| Coconut flour |
112 g |
4 oz |
Weight measurements are always more accurate than volume for flour.
Common Baking Conversions
| Ingredient |
1 cup |
Grams |
| Granulated sugar |
200 g |
|
| Brown sugar (packed) |
220 g |
|
| Powdered/icing sugar |
120 g |
|
| Honey / maple syrup |
340 g |
|
| Rolled oats |
90 g |
|
| Cocoa powder |
85 g |
|
| Chocolate chips |
170 g |
|
| Rice (dry) |
185 g |
|
| Milk |
245 ml / 245 g |
|
| Heavy cream |
240 ml |
|
Oven Temperature Conversions
| Fahrenheit |
Celsius |
Gas Mark |
Description |
| 250°F |
120°C |
½ |
Very slow/low |
| 300°F |
150°C |
2 |
Slow |
| 325°F |
165°C |
3 |
Moderately slow |
| 350°F |
175°C |
4 |
Moderate |
| 375°F |
190°C |
5 |
Moderately hot |
| 400°F |
200°C |
6 |
Hot |
| 425°F |
220°C |
7 |
Very hot |
| 450°F |
230°C |
8 |
Extremely hot |
| 475°F |
245°C |
9 |
Broil/grill range |
| 500°F |
260°C |
10 |
Maximum |
US Liquid Measures Quick Reference
| US |
Metric (approx) |
| 1 teaspoon |
5 ml |
| 1 tablespoon |
15 ml |
| 2 tablespoons (1 fl oz) |
30 ml |
| 1/4 cup (4 tbsp) |
60 ml |
| 1/3 cup |
80 ml |
| 1/2 cup |
120 ml |
| 2/3 cup |
160 ml |
| 3/4 cup |
180 ml |
| 1 cup |
240 ml |
| 2 cups (1 pint) |
475 ml |
| 4 cups (1 quart) |
950 ml |
| 4 quarts (1 gallon) |
3.8 L |
Miscellaneous Length Reference
Human-Scale Quick Reference
| Length |
Approximate |
| Width of thumb |
≈ 1 inch |
| Length of hand (palm to middle finger tip) |
≈ 7 inches |
| Arm span (adult) |
≈ height in inches |
| Stride (walking) |
≈ 2.5 feet |
| Step (pace) |
≈ 2.5–3 feet |
| 1,000 steps |
≈ 0.5 miles |
| 2,000 steps |
≈ 1 mile |
| 10,000 steps |
≈ 5 miles (≈8 km) |
Section 15.1 — The Observatory Almanac
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