Surgical Instrument Measurement & Conversion Tools
Convert common measurements and explore reference charts for surgical instruments and medical tubing. Use the interactive tools below to convert dimensions and review catheter sizing information.
Quick Measurement Converter
Convert between millimeters, centimeters, meters, inches, feet, grams, kilograms, ounces and pounds.
Mass only: ounces here are avoirdupois ounces of mass, not fluid ounces, and mass is never converted to volume.
Result
Enter one value per line. Results keep the order you entered; lines that cannot be read are flagged.
French / Charrière Size Converter
Convert French (Fr) size to external diameter, and the reverse. Commonly used for catheters, sounds and bougies.
External diameter
French size (Fr) = external diameter in mm × 3
External diameter in mm = French size ÷ 3
External diameter in inches = mm ÷ 25.4
| Fr (Ch) | External diameter (mm) | External diameter (cm) | External diameter (inches) |
|---|---|---|---|
| 0.333 | 0.033 | 0.0131 | |
| 0.667 | 0.067 | 0.0262 | |
| 1.000 | 0.100 | 0.0394 | |
| 1.333 | 0.133 | 0.0525 | |
| 1.667 | 0.167 | 0.0656 | |
| 2.000 | 0.200 | 0.0787 | |
| 2.333 | 0.233 | 0.0919 | |
| 2.667 | 0.267 | 0.1050 | |
| 3.000 | 0.300 | 0.1181 | |
| 3.333 | 0.333 | 0.1312 | |
| 3.667 | 0.367 | 0.1444 | |
| 4.000 | 0.400 | 0.1575 | |
| 4.333 | 0.433 | 0.1706 | |
| 4.667 | 0.467 | 0.1837 | |
| 5.000 | 0.500 | 0.1969 | |
| 5.333 | 0.533 | 0.2100 | |
| 5.667 | 0.567 | 0.2231 | |
| 6.000 | 0.600 | 0.2362 | |
| 6.333 | 0.633 | 0.2493 | |
| 6.667 | 0.667 | 0.2625 | |
| 7.000 | 0.700 | 0.2756 | |
| 7.333 | 0.733 | 0.2887 | |
| 7.667 | 0.767 | 0.3018 | |
| 8.000 | 0.800 | 0.3150 | |
| 8.333 | 0.833 | 0.3281 | |
| 8.667 | 0.867 | 0.3412 | |
| 9.000 | 0.900 | 0.3543 | |
| 9.333 | 0.933 | 0.3675 | |
| 9.667 | 0.967 | 0.3806 | |
| 10.000 | 1.000 | 0.3937 | |
| 10.333 | 1.033 | 0.4068 | |
| 10.667 | 1.067 | 0.4199 | |
| 11.000 | 1.100 | 0.4331 | |
| 11.333 | 1.133 | 0.4462 | |
| 11.667 | 1.167 | 0.4593 | |
| 12.000 | 1.200 | 0.4724 | |
| 12.333 | 1.233 | 0.4856 | |
| 12.667 | 1.267 | 0.4987 | |
| 13.000 | 1.300 | 0.5118 | |
| 13.333 | 1.333 | 0.5249 | |
| 13.667 | 1.367 | 0.5381 | |
| 14.000 | 1.400 | 0.5512 | |
| 14.333 | 1.433 | 0.5643 | |
| 14.667 | 1.467 | 0.5774 | |
| 15.000 | 1.500 | 0.5906 | |
| 15.333 | 1.533 | 0.6037 | |
| 15.667 | 1.567 | 0.6168 | |
| 16.000 | 1.600 | 0.6299 | |
| 16.333 | 1.633 | 0.6430 | |
| 16.667 | 1.667 | 0.6562 | |
| 17.000 | 1.700 | 0.6693 | |
| 17.333 | 1.733 | 0.6824 | |
| 17.667 | 1.767 | 0.6955 | |
| 18.000 | 1.800 | 0.7087 | |
| 18.333 | 1.833 | 0.7218 | |
| 18.667 | 1.867 | 0.7349 | |
| 19.000 | 1.900 | 0.7480 | |
| 19.333 | 1.933 | 0.7612 | |
| 19.667 | 1.967 | 0.7743 | |
| 20.000 | 2.000 | 0.7874 |
No sizes match that search.
Common Measurement Conversions
Common Length Conversions
Quick reference for common instrument dimensions.
| Millimeters (mm) | Centimeters (cm) | Inches (in) |
|---|---|---|
| 1 | 0.1 | 0.0394 |
| 2 | 0.2 | 0.0787 |
| 3 | 0.3 | 0.1181 |
| 4 | 0.4 | 0.1575 |
| 5 | 0.5 | 0.1969 |
| 6 | 0.6 | 0.2362 |
| 8 | 0.8 | 0.3150 |
| 10 | 1 | 0.3937 |
| 12 | 1.2 | 0.4724 |
| 15 | 1.5 | 0.5906 |
| 20 | 2 | 0.7874 |
| 25 | 2.5 | 0.9843 |
| 30 | 3 | 1.1811 |
| 40 | 4 | 1.5748 |
| 50 | 5 | 1.9685 |
| 60 | 6 | 2.3622 |
| 75 | 7.5 | 2.9528 |
| 80 | 8 | 3.1496 |
| 100 | 10 | 3.9370 |
| 120 | 12 | 4.7244 |
| 125 | 12.5 | 4.9213 |
| 150 | 15 | 5.9055 |
| 175 | 17.5 | 6.8898 |
| 200 | 20 | 7.8740 |
| 250 | 25 | 9.8425 |
| 300 | 30 | 11.8110 |
No values match that filter.
Common Mass Conversions
Grams converted to kilograms, avoirdupois ounces and pounds.
| Grams (g) | Kilograms (kg) | Ounces (oz) | Pounds (lb) |
|---|---|---|---|
| 1 | 0.001 | 0.0353 | 0.0022 |
| 2 | 0.002 | 0.0705 | 0.0044 |
| 5 | 0.005 | 0.1764 | 0.0110 |
| 10 | 0.01 | 0.3527 | 0.0220 |
| 15 | 0.015 | 0.5291 | 0.0331 |
| 20 | 0.02 | 0.7055 | 0.0441 |
| 25 | 0.025 | 0.8818 | 0.0551 |
| 30 | 0.03 | 1.0582 | 0.0661 |
| 40 | 0.04 | 1.4110 | 0.0882 |
| 50 | 0.05 | 1.7637 | 0.1102 |
| 60 | 0.06 | 2.1164 | 0.1323 |
| 75 | 0.075 | 2.6455 | 0.1653 |
| 100 | 0.1 | 3.5274 | 0.2205 |
| 150 | 0.15 | 5.2911 | 0.3307 |
| 200 | 0.2 | 7.0548 | 0.4409 |
| 250 | 0.25 | 8.8185 | 0.5512 |
| 300 | 0.3 | 10.5822 | 0.6614 |
| 400 | 0.4 | 14.1096 | 0.8818 |
| 500 | 0.5 | 17.6370 | 1.1023 |
| 750 | 0.75 | 26.4555 | 1.6535 |
| 1000 | 1 | 35.2740 | 2.2046 |
No values match that filter.
Instrument Measurement Helper
See one length in several units side by side. This converts a number you enter; it does not measure or verify a physical instrument.
- 75 mm
- 7.5 cm
- 2.9528 in
- 0.2461 ft
About These Measurements
Understanding the Measurements
Instrument dimensions are linear measurements, normally given in millimeters or centimeters, and in inches in some catalogues. Mass is a separate quantity, measured in grams, kilograms, ounces and pounds. The ounce used here is the avoirdupois ounce of mass, not the fluid ounce. One inch is exactly 25.4 mm.
Understanding French/Charrière Size
French (Fr), Charrière (Ch or CH) and French gauge (FG) describe the external diameter of tubing such as catheters, sounds and bougies. The size is the diameter in millimeters multiplied by 3, so one size step is one third of a millimeter. It does not describe the internal lumen. This page does not convert English or American gauge sizes; use the sizing stated in the specification of the specific instrument.
Confirming Instrument Specifications
These tools give calculated values only. Confirm exact dimensions, sizes and tolerances in the individual product specification, or ask Hospitime through the Enquiry page, before ordering.
Sources: the inch and foot are defined exactly in NIST SP 811, Appendix B (1 in = 2.54 cm, 1 ft = 0.3048 m). The French/Charrière relationship (external diameter, 1 mm = 3 Ch) follows the EAUN catheterisation guideline. Mass factors used: 1 lb = 0.45359237 kg; 1 oz = 28.349523125 g.
Related Instrument Categories
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