Math in Welding

Math is an essential part of the welding process. Welders use math to make precise measurements, fabricate projects, calculate correct settings based on variables, give accurate and fair estimates, and use logic to speed up fabrication processes.

Measurement Systems

The US customary system (e.g. inch, foot, yard, mile) is the most commonly used measurement system in the US. Most weld shops use this system of units. The most basic unit of distance is an inch, and it builds from there: 12 inches is 1 foot, 3 feet is 1 yard, and 1760 yards is 1 mile. Most jobs are done using inches and/or feet. Inches can be broken up into fractions (typically multiples of 8). The standard notation (e.g. 6′-2″) follows several rules:

• If both feet and inches are noted, feet are noted first. (Sometimes only inches are used.)
• If both feet and inches are noted, they are separated with a dash.
• Feet are marked with an apostrophe (e.g. 6′) and inches with quotation marks (e.g. 13″).

The international system of units, also known as the SI system or the metric system, is recognized by all countries and has been standardized across the world. The most basic unit of distance is a millimeter, and subsequent units are multiples of 10: 10 millimeters is 1 centimeter, 10 centimeters is 1 meter. This is a much simpler system than the US customary system because it is based on decimals.

Linear Measurements

A linear measurement is a measurement taken in a straight line, usually with tape measures or rulers. It is important to be as accurate as possible when measuring and to check your measurement twice. If you are measuring from a blueprint, verify that the number you are reading is correct before cutting out your parts.

A tolerance (an acceptable range of deviation) may allow for a final product that is over or under the ideal measurement. Tolerances are usually given by a +/- or ± symbol, with the combination of the plus and minus signs demonstrating that you can go over or under the measurement given, but it is important to stay within that tolerance.

Converting Units

The most common conversions welders may have to do are below. Calculators are encouraged if you need them! It’s better to be accurate than to be showy.

• To convert from feet to inches, multiply by 12.
• To convert from inches to feet, divide by 12.
• To convert from inches to millimeters, multiply by 25.4.
• To convert from millimeters to inches, divide by 25.4.