Measurement Conversions

Common Surgical Instrument Sizes

Do you need to convert millimeters to inches? Inches to centimeters? Ounces to grams? Perhaps you need to compare the diameters of various catheters, sounds or bougies using the French, English or American scales.

Stainless Steel Instruments

Ten millimeters = one centimeter.
To convert inches to centimeters, multiply inches in decimals by 2.54.
To convert centimeters to inches, multiply centimeters by .3937.
To convert millimeters to inches, multiply millimeters by .03937.
The standard French, or Charriere, Scale (abbreviated Fr.) is generally used in the size calibration of catheters and other tubular instruments. It is based on the metric system, with each unit being approximately 0.33 mm in diameter between consecutive sizes.

Download Conversion Chart

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Liquid Conversion

UOM	fluid oz.	quarts	gallons	ml	liters
Multiplier	29.57	0.95	3.79	0.03	1.06 0.26
Converts To	ml	litres	liters	fluid.oz	quartz gallons

COMPARATIVE SCALES OR GAUGES

Used in Measuring the Diameters of Catheters, Sounds and Bougies

Diameters in MM	American	French	English
1/3	-	1	-
1/2	1	-	-
2/3	-	2	-
1	2	3	-
1-1/3	-	4	-
1-1/2	3	-	-
1-2/3	-	5	-
2	4	5	-
2-1/3	-	7	1
2-1/2	5	-	-
2-2/3	-	8	2
3	6	9	3
3-1/3	-	10	-
3-1/2	7	-	-
3-2/3	-	11	4
4	8	12	5
4-1/3	-	13	-
4-1/2	9	-	-
4-2/3	-	14	-
5	10	15	6
5-1/3	-	16	7
5-1/2	11	-	-
5-2/3	-	17	8
6	12	18	9
6-1/3	-	19	10
6-1/2	13	-	-
6-2/3	-	20	11

Diameters in MM	American	French	English
7	14	21	-
7-1/3	1	22	12
7-1/2	15	-	-
7-2/3	-	23	13
8	16	24	-
8-1/3	-	25	14
8-1/2	17	-	-
8-2/3	-	26	15
9	18	27	16
9-1/3	-	28	17
9-1/2	19	-	-
9-2/3	-	29	-
10	20	30	18
10-1/3	-	31	19
10-1/2	21	-	-
10-2/3	-	32	20
11	22	33	21
11-1/3	-	34	22
11-1/2	23	-	-
11-2/3	-	35	23
12	24	36	24
12-1/3	-	37	25
12-1/2	25	-	-
12-2/3	-	38	26
13	26	39	27
13-1/3	-	40	28