Short answer
Multiply kg per metre by 0.67197 to get pounds per foot. To go the other way, multiply lb/ft by 1.48816. For example, an IPE 300 at 42.2 kg/m is 28.36 lb/ft, and a W12x26 at 26 lb/ft is 38.7 kg/m.
Where the factor comes from
One kilogram is 2.20462 pounds and one metre is 3.28084 feet. Dividing the first by the second gives 2.20462 / 3.28084 = 0.67197. The reverse is 1 / 0.67197 = 1.48816.
| From | To | Multiply by |
|---|---|---|
| kg/m | lb/ft | 0.67197 |
| lb/ft | kg/m | 1.48816 |
| mm | in | divide by 25.4 |
| m | ft | multiply by 3.28084 |
| tonne | short ton | multiply by 1.10231 |
Worked examples
| Section | Standard | kg/m | lb/ft |
|---|---|---|---|
| 203x133x25 UB | UK | 25.1 | 16.87 |
| IPE 300 | EN | 42.2 | 28.36 |
| 250UB25.7 | AS/NZS | 25.7 | 17.27 |
| W12x26 | AISC | 38.7 | 26.0 |
Check one by hand: 42.2 x 0.67197 = 28.36. For a whole beam, convert the length as well. A 6 m IPE 300 is 6 x 42.2 = 253.2 kg, which is about 558 lb. Metric tonne to short ton is a separate conversion (see below).
What is the difference between a tonne and a ton?
A metric tonne is 1,000 kg, about 2,204.6 lb. A US short ton is 2,000 lb, about 907 kg. The tonne is about 10 percent heavier. When you convert quantities between a metric drawing set and a US price list, convert the weight first and then apply the price, and write the unit in every column of the spreadsheet. A bid that mixes the two without saying so is wrong by 10 percent before anyone prices anything.
Common conversion mistakes
- Converting kg/m to lb/ft by multiplying by 2.2046. That converts mass but ignores that you also changed metres to feet, and overstates weight by a factor of 3.28.
- Treating a metric designation's final number as lb/ft. In 203x133x25 UB the 25 is kg/m.
- Converting a rounded value twice. Use the table value for each section when possible.
- Assuming a metric section and its nearest imperial section are the same piece. They are not interchangeable.
SteelFlo does the conversion for you. Metric drawings stay in metric, and you can price in your own currency and unit. The same factor is used in every shape page, which shows both units.
A quick lookup table
| kg/m | lb/ft |
|---|---|
| 10 | 6.72 |
| 20 | 13.44 |
| 25 | 16.80 |
| 30 | 20.16 |
| 40 | 26.88 |
| 50 | 33.60 |
| 75 | 50.40 |
| 100 | 67.20 |
These are straight conversions of round numbers. For a real section, use the weight in the table for that section, not a conversion of the rounded name.
How do you do it in a spreadsheet?
Put the factor in one named cell, say KG_M_TO_LB_FT = 0.67197, and refer to it everywhere. Never type 0.67 in one place and 0.672 in another. Keep separate columns for the original unit and the converted unit, and label them. If you work across standards, add a units column per line so the total column can convert each line consistently before summing.
Avoid converting twice. If your source is metric and your output is imperial, convert once, at the end of the calculation, not at each step.
Do you need to convert at all?
Often not. If the drawings are metric and your supplier quotes per tonne, stay in metric. Convert only when you need to compare with an imperial price list or report to an imperial client. SteelFlo keeps metric jobs in metric, shows weights in the units of the job, and the calculator and shape pages show both side by side.
Look up the sizes
Stop counting steel by hand.
Upload your drawing set and SteelFlo puts a box on every steel label it finds, on every page. You verify the boxes and export a bill of materials.