Nobody walks through an overseas train depot or distribution warehouse holding a scientific mass conversion calculator. When you need a quick mental math shortcut that delivers immediate accuracy within a fraction of a percent, the standard "double plus ten percent" trick works cleanly.
Take the metric figure and double it. Doubling 36 gives you 72. Next, calculate 10 percent of that doubled figure by sliding the decimal point one position to the left, which gives you 7.2. Finally, add those two integers together:
72 + 7.2 = 79.2 lbs
This rapid mental estimate lands within 0.17 pounds of the true mathematical value. For general physical intuition, it provides a 99.8% accurate reading in three seconds flat without pulling out a smartphone.
