Everyday Reference Tables

Quick-look conversions and reference data for daily life.

Time Zones: 24 Major Cities

All offsets shown as UTC+/−. Times shift during Daylight Saving Time (DST) where observed — check a live source for current offsets.

City	Country	Standard Offset	DST Offset	Notes
Honolulu	USA (Hawaii)	UTC−10	No DST	Hawaii never observes DST
Anchorage	USA (Alaska)	UTC−9	UTC−8	DST observed Mar–Nov
Los Angeles	USA	UTC−8	UTC−7	Pacific Time
Denver	USA	UTC−7	UTC−6	Mountain Time
Chicago	USA	UTC−6	UTC−5	Central Time
New York	USA	UTC−5	UTC−4	Eastern Time
São Paulo	Brazil	UTC−3	UTC−2 (summer)	Southern Hemisphere DST
London	UK	UTC±0	UTC+1	GMT / BST
Paris	France	UTC+1	UTC+2	CET / CEST
Berlin	Germany	UTC+1	UTC+2	CET / CEST
Cairo	Egypt	UTC+2	No DST	Egypt suspended DST
Istanbul	Turkey	UTC+3	No DST	Permanently UTC+3 since 2016
Moscow	Russia	UTC+3	No DST	Russia abolished DST in 2014
Dubai	UAE	UTC+4	No DST	Gulf Standard Time
Karachi	Pakistan	UTC+5	No DST	PKT
Delhi	India	UTC+5:30	No DST	India has a 30-min offset
Dhaka	Bangladesh	UTC+6	No DST	BST
Bangkok	Thailand	UTC+7	No DST	Indochina Time
Singapore	Singapore	UTC+8	No DST	SST
Beijing	China	UTC+8	No DST	All of China uses one time zone
Tokyo	Japan	UTC+9	No DST	JST — Japan has never used DST
Sydney	Australia	UTC+10	UTC+11	AEST / AEDT (Oct–Apr DST)
Auckland	New Zealand	UTC+12	UTC+13	NZST / NZDT
Fiji	Fiji	UTC+12	UTC+13	DST observed Nov–Jan

Converting between two cities: Subtract the origin offset from the destination offset to find the difference. Example: New York (UTC−5) to Tokyo (UTC+9) = +14 hours.

Clothing Size Conversions

Women's Shoes

US	UK	EU	Japan (cm)
5	2.5	35	22
5.5	3	35.5	22.5
6	3.5	36	23
6.5	4	37	23.5
7	4.5	37.5	24
7.5	5	38	24.5
8	5.5	38.5	25
8.5	6	39	25.5
9	6.5	40	26
9.5	7	40.5	26.5
10	7.5	41	27
11	8.5	42	28

Men's Shoes

US	UK	EU	Japan (cm)
6	5.5	39	24.5
6.5	6	39.5	25
7	6.5	40	25.5
7.5	7	40.5	26
8	7.5	41	26.5
8.5	8	42	27
9	8.5	42.5	27.5
9.5	9	43	28
10	9.5	44	28.5
10.5	10	44.5	29
11	10.5	45	29.5
12	11.5	46	30.5
13	12.5	47	31.5

Women's Clothing (Tops / Dresses)

US	UK	EU	Asian (approx.)
0 (XS)	4	32	XS / 155/80A
2 (XS)	6	34	XS / 155/80A
4 (S)	8	36	S / 160/84A
6 (S)	10	38	S / 160/84A
8 (M)	12	40	M / 165/88A
10 (M)	14	42	M / 165/88A
12 (L)	16	44	L / 170/92A
14 (L)	18	46	L / 170/92A
16 (XL)	20	48	XL / 175/96A
18 (2XL)	22	50	2XL / 180/100A
20 (3XL)	24	52	3XL

Asian sizing varies significantly by brand and country. Measurements in the format height/bust are common in China/Korea.

Men's Shirts (Neck / Chest)

US/UK Neck	EU Neck (cm)	US/UK Chest	EU Chest (cm)	Size Label
14	36	34	86	XS
14.5	37	36	91	S
15	38	38	96	S
15.5	39–40	40	101	M
16	41	42	107	L
16.5	42	44	112	L
17	43	46	117	XL
17.5	44–45	48	122	2XL
18	46	50	127	3XL

Men's Pants (Waist)

US/UK (inches)	EU (cm)	Asian (approx.)
28	71	S
30	76	M
32	81	L
34	86	XL
36	91	2XL
38	96	3XL
40	102	4XL

Children's Clothing (Age-Based)

Age	US Size	EU Size	Height (cm)	Weight (kg approx.)
0–3 months	3M	56–62	56–62	3–5
3–6 months	6M	62–68	62–68	5–7
6–12 months	12M	68–80	68–80	7–10
12–18 months	18M	80–86	80–86	10–12
2 years	2T	92	86–92	12–14
3 years	3T	98	92–98	14–16
4 years	4T	104	98–104	16–18
5 years	5	110	104–110	18–20
6 years	6	116	110–116	20–22
7 years	7	122	116–122	22–25
8 years	8	128	122–128	25–28
10 years	10	140	134–140	30–34
12 years	12	152	146–152	38–43

Ring Sizes

US	UK / Australia	EU (mm circumference)	Diameter (mm)
4	H	46.8	14.9
4.5	I	47.8	15.3
5	J–K	49.3	15.7
5.5	K–L	50.6	16.1
6	L–M	51.9	16.5
6.5	M–N	53.1	16.9
7	N–O	54.4	17.3
7.5	O–P	55.7	17.7
8	P–Q	57.0	18.1
8.5	Q–R	58.3	18.6
9	R–S	59.5	18.9
9.5	S–T	60.8	19.4
10	T–U	62.1	19.8
11	V–W	64.6	20.6
12	X–Y	67.2	21.4

To measure ring size at home: Wrap a thin strip of paper around the base of your finger, mark where it overlaps, measure the length in mm — that is your circumference. Match to the EU column above.

Paper Sizes

ISO 216 "A" Series

Size	mm	inches	Common Use
A0	841 × 1189	33.1 × 46.8	Large posters, architectural drawings
A1	594 × 841	23.4 × 33.1	Posters, flip charts
A2	420 × 594	16.5 × 23.4	Posters, large diagrams
A3	297 × 420	11.7 × 16.5	Tabloid equivalent, spreadsheets
A4	210 × 297	8.3 × 11.7	Standard document (most of world)
A5	148 × 210	5.8 × 8.3	Notepads, small booklets
A6	105 × 148	4.1 × 5.8	Postcards, index cards

Each A size is exactly half of the one above. A0 has an area of exactly 1 square meter.

North American Sizes

Name	mm	inches	Common Use
Letter	215.9 × 279.4	8.5 × 11	Standard US/Canada document
Legal	215.9 × 355.6	8.5 × 14	Legal documents, contracts
Tabloid / Ledger	279.4 × 431.8	11 × 17	Newspapers, large spreadsheets

Birthstones

Month	Traditional	Modern
January	Garnet	Garnet
February	Amethyst	Amethyst
March	Bloodstone	Aquamarine
April	Diamond	Diamond
May	Emerald	Emerald
June	Pearl	Alexandrite (also Pearl, Moonstone)
July	Ruby	Ruby
August	Sardonyx	Peridot (also Spinel)
September	Sapphire	Sapphire
October	Opal	Tourmaline
November	Topaz	Citrine
December	Turquoise	Blue Topaz (also Tanzanite, Zircon)

Traditional list from the 1912 American National Jewelers Association. Modern list revised by the American Gem Society.

Anniversary Gifts: Traditional & Modern

Year	Traditional	Modern
1st	Paper	Clocks
2nd	Cotton	China
3rd	Leather	Crystal / Glass
4th	Linen / Silk	Appliances
5th	Wood	Silverware
6th	Candy / Iron	Wood
7th	Wool / Copper	Desk Sets
8th	Pottery / Bronze	Linens / Lace
9th	Pottery / Willow	Leather
10th	Tin / Aluminum	Diamond Jewelry
11th	Steel	Fashion Jewelry
12th	Silk / Linen	Pearls
13th	Lace	Textiles / Furs
14th	Ivory	Gold Jewelry
15th	Crystal	Watches
20th	China	Platinum
25th	Silver	Silver
30th	Pearl	Diamond
35th	Coral	Jade
40th	Ruby	Ruby
45th	Sapphire	Sapphire
50th	Gold	Gold
55th	Emerald	Emerald
60th	Diamond	Diamond
65th	Blue Sapphire	Blue Sapphire
70th	Platinum	Platinum
75th	Diamond / Gold	Diamond / Gold

Tipping Customs by Country

Country	Restaurants	Taxis	Other	Notes
USA	15–20% (mandatory in practice)	15–20%	Bartenders $1–2/drink; hotel housekeeping $2–5/night	Tipping is effectively compulsory; servers may earn below minimum wage
Canada	15–20%	10–15%	Similar to USA	Tax-inclusive prices; tip on pre-tax amount
UK	10–15% (check for service charge)	Round up or 10%	Not expected for drinks at pub bar	Service charge is often added automatically — check bill first
France	Service compris (included) — add 1–5% if pleased	Round up	Not widely expected	"Pourboire" is optional and truly appreciated rather than expected
Germany	5–10%; round up to nearest euro	Round up	Cafes: round up	Say "stimmt so" (keep the change) when paying; do not leave coins on table
Japan	Never tip	Never tip	Never tip	Tipping is considered rude; can cause embarrassment or be refused
China	Not traditional; increasingly 10–15% in tourist areas	Not expected	Hotel: not expected	High-end hotels and Western restaurants may add service charge
Australia	Not required; 10% appreciated	Not required	Not required	Minimum wage is high; tipping is optional and not expected
Mexico	10–15%	10%	Hotel staff: 20–50 pesos	Always tip in cash; many workers earn very low base wages
Brazil	10% service charge usually included	Round up	Not widely expected	Check bill for "taxa de serviço" before adding extra
UAE / Dubai	10–15% in restaurants	Round up	Hotel: 10 AED per service	Service charge often included in hotels; appreciate the gesture
India	10% in restaurants	Round up	Hotel porter: ₹20–50	Varies widely by location; street food/local chai: not expected
Italy	Coperto (cover charge) is normal; no further tip required	Round up	Espresso bar: leave coins	Coperto is ₹1–3 per person; it is for bread and table service
Spain	5–10% appreciated; not required	Round up	Not widely expected	Spanish locals tip modestly; tourists expected to be generous
South Africa	10–15%	10%	Petrol station attendants: R5–10	Service industry wages are low; tipping is important

Battery Sizes and Common Uses

Size	Dimensions (mm)	Voltage	Chemistry	Common Uses
AAA	10.5 dia × 44.5	1.5V	Alkaline / NiMH	Remote controls, small toys, flashlights, blood pressure monitors
AA	14.5 dia × 50.5	1.5V	Alkaline / NiMH	Most common — cameras, clocks, TV remotes, wireless mice, flashlights
C	26.2 dia × 50.0	1.5V	Alkaline	Portable radios, flashlights, toys, baby monitors
D	34.2 dia × 61.5	1.5V	Alkaline	High-drain devices: large flashlights, boomboxes, emergency radios
9V	26.5 × 17.5 × 48.5	9V	Alkaline / Lithium	Smoke detectors, guitar effects pedals, multimeters, walkie-talkies
CR2032	20 dia × 3.2	3V	Lithium (coin cell)	Watches, key fobs, calculators, computer CMOS memory, small LED lights
CR2025	20 dia × 2.5	3V	Lithium (coin cell)	Watches, key fobs, calculators — thinner version of CR2032

Notes: - Rechargeable NiMH batteries output ~1.2V vs alkaline's 1.5V — compatible with most devices - CR2032 and CR2025 are interchangeable in many devices (same diameter, slightly different thickness) - "CR" = Lithium chemistry; first two digits = diameter; last two = thickness in tenths of mm

Light Bulb Equivalency Chart

LED equivalents produce the same light (lumens) as old incandescent bulbs while using significantly less power.

Incandescent (Old)	LED Equivalent	Lumens	Best Use
25W	2–3W	250 lm	Night lights, decorative lamps
40W	5–6W	450 lm	Bedside lamps, closets
60W	8–10W	800 lm	Standard table and floor lamps
75W	10–13W	1,100 lm	Kitchens, workspaces
100W	14–18W	1,600 lm	Bright overhead lighting
150W	22–26W	2,600 lm	Very bright workspace, garage

Color Temperature Reference: - 2700K–3000K: Warm white (yellowish) — cozy, residential rooms - 3500K–4100K: Cool white (neutral) — kitchens, offices - 5000K–6500K: Daylight (bluish-white) — workshops, reading tasks

CRI (Color Rendering Index): 90+ CRI renders colors most accurately. Relevant for art studios, makeup areas.

Mohs Hardness Scale

The Mohs scale rates a mineral's resistance to scratching, from 1 (softest) to 10 (hardest). A material can scratch anything softer than itself.

Hardness	Mineral	Common Reference Object
1	Talc	Easily scratched by fingernail; feels greasy
2	Gypsum	Can be scratched by fingernail (hardness 2.5)
2.5	—	Fingernail
3	Calcite	Scratched easily by a copper coin
3.5	—	Copper coin
4	Fluorite	Scratched by a steel knife but not a fingernail
5	Apatite	Barely scratched by a steel knife
5.5	—	Steel knife / glass
6	Orthoclase feldspar	Scratches glass easily
6.5	—	Steel file
7	Quartz	Scratches glass and most steels; common sand
8	Topaz	Scratched only by corundum and diamond
9	Corundum (sapphire/ruby)	Scratched only by diamond
10	Diamond	Scratches everything; hardest natural material

Practical applications: - Window glass: ~5.5 — can be scratched by keys (which are usually steel, ~6) - Steel file: ~6.5 — useful field test tool - Common sand (quartz): 7 — reason why sand scratches car paint (paint ~2–3) - Human tooth enamel: ~5 - Human bone: ~5

pH Scale: 0–14

The pH scale measures acidity vs. alkalinity. 7 = neutral; below 7 = acidic; above 7 = basic (alkaline).

pH	Substance	Category
0	Battery acid (H₂SO₄)	Strongly acidic
1	Hydrochloric acid (gastric acid)	Strongly acidic
2	Lemon juice, vinegar	Strongly acidic
2.5	Soft drinks (cola)	Strongly acidic
3	Orange juice, apple juice	Acidic
3.5	Tomato juice	Acidic
4	Beer, wine	Acidic
4.5	Tomatoes, acid rain	Acidic
5	Black coffee, bananas	Mildly acidic
5.5	Urine (typical)	Mildly acidic
6	Milk	Mildly acidic
6.5	Saliva	Near neutral
7.0	Pure water	Neutral
7.4	Human blood	Very slightly basic
8	Seawater, baking soda solution	Mildly basic
8.5	Antacid tablets	Mildly basic
9	Soap, hand sanitizer	Basic
10	Milk of magnesia	Moderately basic
11	Ammonia (household cleaner)	Basic
12	Soapy water, bleach (diluted)	Strongly basic
13	Oven cleaner, lye	Strongly basic
14	Sodium hydroxide (NaOH)	Strongly basic

Notes: - Each step on the pH scale is a factor of 10 in concentration (pH 4 is 10x more acidic than pH 5) - The human body tightly regulates blood pH at ~7.35–7.45; deviations of ±0.2 are medically significant - Soil pH affects plant growth: most vegetables prefer 6.0–7.0; blueberries prefer 4.5–5.5 - Swimming pools are maintained at pH 7.2–7.6 to prevent skin/eye irritation and equipment corrosion

See also: 15-reference-tables/cooking-measurements.md, 15-reference-tables/unit-conversions.md