How to Convert Kilograms and Pounds in Your Workout Log

To convert pounds to kilograms, multiply by 0.45359237. To convert kilograms to pounds, divide by 0.45359237. Keep the original recorded value and unit alongside the conversion so you can tell what the equipment actually displayed.

The NIST mass calibration reference gives the exact relationship: one avoirdupois pound equals 0.45359237 kilogram. The conversion is fixed; the precision of the weight label or your original entry is a separate matter.

Keep source values and converted values separate

Suppose you visit a gym where a dumbbell is labeled 25 lb. A useful record is “25 lb per dumbbell; approximately 11.34 kg per dumbbell.” Do not replace the source label with “11 kg” and later assume that was the equipment you used.

If the next gym has a 12 kg dumbbell, that is a different labeled load. It is not an exact equivalent of 25 lb. Converting units helps describe a record; it does not choose a suitable training load or prove that two pieces of equipment are interchangeable.

Three conversions you can check

• 25 lb × 0.45359237 = 11.33980925 kg, or approximately 11.34 kg.
• 20 kg ÷ 0.45359237 = approximately 44.09245 lb, or 44.09 lb to two decimal places.
• 100 lb × 0.45359237 = 45.359237 kg, or approximately 45.36 kg.

The extra decimal places come from arithmetic. They do not mean a gym weight was physically measured to that precision. For a readable log, choose a consistent display precision and preserve the original label.

The kg–lb reference CSV contains these examples and blank columns for your own records. The example conversion values are fixed values, not formulas that update when you edit the CSV.

Convert the same thing on both sides

Units are only one part of the load convention. A pair of dumbbells labeled 20 lb each has 40 lb of combined labeled mass. Converting one dumbbell gives approximately 9.07 kg; converting the pair gives approximately 18.14 kg. Both calculations are valid, but they describe different quantities.

Before comparing entries, check whether each number means per dumbbell, combined dumbbells, a barbell total or a machine’s displayed load. Read how to log dumbbell weight if older entries do not make that clear.

Avoid a false jump in your history

A record that changes from “40” to “90” may look like a large increase if the units are missing. But 40 kg is approximately 88.18 lb. You need the original units before interpreting that change.

Do not infer the unit from the size of the number alone. Check the original note or equipment label. If it cannot be recovered, mark the entry as unit unknown and leave it out of a numerical comparison that requires a known unit.

Repeatedly converting a rounded value back and forth can also introduce small differences. Always calculate from the preserved source value instead of converting yesterday’s rounded display again.

Keep equipment differences visible

A kg-to-lb conversion only changes units. It does not reconcile different cable ratios, machine designs or logging conventions. Compare matching equipment and definitions before using converted records to describe a personal best.

For future sessions, write the unit at entry time and review a surprising number before treating it as progress. The workout comparison guide covers the wider context, and Gymr’s workout tracker provides a place to maintain your workout history.