Measurements

Fluid Measurement

• 1 quart = 32 ounces (fluid) = 2 pints = 1/4 gallon = 57 cubic inches
• 1 gallon = 4 quarts = 128 ounces (fluid) = 3.78 litre and 231 cubic inches = 0.134 cubic feet
• 1 litre = 1,000 cc (slightly more than 1 quart U.S.) = 0.264 U.S. gallons
• 1 cubic foot = 7.481 U.S. gallons = 1,728 cubic inches
• 1 imperial gallon = 1.2 U.S. gallons = 4.59 litre = 277.27 cubic inches

Douzieme Gauge

The douzieme gauge used by watchmakers and sometimes by jewelers is also called a spring gauge and degree gauge. Douzieme in French means 1/12.

• 1 douzieme = 1/12 ligne (or line) = 0.0074″ = 0.188mm
• 1 ligne = 12 douzieme = 0.0888″ = 2.256mm

Length Conversion

To convert:
Millimetres to inches	Multiply by	0.0393701
Inches to millimetres	Multiply by	25.4
Metres to inches	Multiply by	39.3701
Inches to metres	Multiply by	0.0254

• 1 inch = 25.4 millimetres
• 1 millimetre = 0.0393 inch
• 1 metre = 1,000,000 microns
• 1 micron = 0.000039 inch

Area and Volume Conversion

To convert:
Square inches to square millimetres	Multiply by	645.16
Square inches to square decimetres	Multiply by	0.064516
Square decimetres to square inches	Multiply by	15.50
Square millimetres to square inches	Multiply by	0.00155
Cubic inches to cubic centimetres	Multiply by	16.3871
Cubic centimetres to cubic inches	Multiply by	0.061024

Rules Relating to Circles

• The circumference of a circle is the diameter x 3.1416.
• The diameter of a circle is the circumference multiplied by .31831.
• The area of a circle is the diameter x itself x .7854.
• A circle is .7854 times as heavy as a square of the same size. The loss in cutting a circle from a square is .2146 of the weight of the square.

Stone Conversions

Carat Size	Round Shape MM		Carat Size	Round Shape MM		Carat Size	Round Shape MM
.005	1.0		.11	3.1		.40	4.8
.01	1.3		.12	3.2		.50	5.2
.015	1.5		.14	3.3		.60	5.4
.02	1.7		.15	3.4		.65	5.6
.025	1.8		.16	3.5		.75	5.8
.03	2.0		.17	3.6		.80	6.0
.035	2.1		.18	3.7		1.00	6.5
.04	2.2		.20	3.8		1.25	7.0
.05	2.4		.22	3.9		1.33	7.2
.06	2.5		.23	4.0		1.50	7.4
.07	2.7		.25	4.1		1.75	7.8
.08	2.8		.30	4.2		2.00	8.2
.09	2.9		.33	4.4		2.50	8.8
.10	3.0		.38	4.6		3.00	9.4

Peripheral or Surface Speed (in Feet/Min)

RPM	1″ Diameter	4″ Diameter	6″ Diameter
900	235	950	1400
1150	300	1200	1800
1200	315	1250	1900
1500	400	1550	2350
1750	450	1800	2750
2000	525	2100	3100
2400	625	2500	3800
2800	730	2900	4400
3000	785	3100	4700
3200	840	3350	5000
3450	900	3600	5400
3750	980	3900	5900
4000	1045	4200	6300
4500	1180	4700	7200

Fineness of Gold (Karats)

9K	.3750		17K	.7083
10K	.4167		18K	.7500
11K	.4583		19K	.7917
12K	.5000		20K	.8333
13K	.5417		21K	.8750
14K	.5833		22K	.9167
15K	.6250		23K	.9583
16K	.6667		24K	1.000

Wire and Drill Sizes

B&S	mm	Inches Thou.	Inches Fractions	Drill Size		B&S	mm	Inches Thou.	Inches Fractions	Drill Size
0	8.5	.325	21/64			16	1.29	.050		54
1	7.35	.289	9/32			17	1.15	.045	3/64	55
2	6.54	.258	1/4			18	1.02	.040		56
3	5.83	.229	7/32	1		19	.912	.036		60
4	5.19	.204	13/64	6		20	.813	.032	1/32	65
5	4.62	.182	3/16	15		21	.724	.029		67
6	4.11	.162	5/32	20		22	.643	.025		70
7	3.67	.144	9/64	27		23	.574	.023		71
8	3.26	.129	1/8	30		24	.511	.020		74
10	2.59	.102		38		25	.455	.018		75
11	2.30	.090	3/32	43		26	.404	.016	1/64	77
12	2.05	.080	5/64	46		27	.361	.014		78
13	1.83	.072		50		28	.330	.013		79
14	1.63	.064	1/16	51		29	.279	.011		80
15	1.45	.057		52		30	.254	.010

Ring Size

Size	Inside Diameter Inch	Inside Diameter mm		Size	Inside Diameter Inch	Inside Diameter mm
1	.486	12.344		7 1/2	.694	17.628
1 1/2	.502	12.751		8	.710	18.034
2	.518	13.157		8 1/2	.7265	18.453
2 1/2	.534	13.564		9	.743	18.872
3	.550	13.970		9 1/2	.759	19.279
3 1/2	.566	14.376		10	.778	19.761
4	.582	14.783		10 1/2	.794	20.168
4 1/2	.598	15.189		11	.811	20.599
5	.6141	15.597		11 1/2	.8271	21.008
5 1/2	.6300	16.002		12	.843	21.412
6	.6455	16.396		12 1/2	.859	21.819
6 1/2	.662	16.815		13	.875	22.225
7	.678	17.221

File Teeth Count Teeth

Count by Size Number on Files Used by Jewelers

00 = coarsest; 6 = finest

	Size No.	Teeth per inch upcut
Needle and	00	51
Escapement Files	0	64
4-7 3/4″	1	79
	2	97
	3	117
	4	142
	6	213