A worked example: 100 Nm to pound-feet for a lug nut spec
Running 100 Nm through the torque converter's real formula, converting to pound-feet, returns 73.756215 lb·ft — a torque spec in the range many manufacturers list for wheel lug nuts. Running 1 lb·ft the other direction, converted to newton-meters, returns 1.355818 N·m, matching the converter's own worked example.
The formula: multiply by the from-unit-to-newton-meter factor, divide by the to-unit factor
The converter treats newton-meters as the base unit and stores every other torque unit as a factor of one newton-meter: 1 lb·ft = 1.3558179483314004 N·m. A conversion is amount × (from-unit-to-Nm factor) ÷ (to-unit-to-Nm factor). For 100 Nm to lb·ft, that's 100 × 1 ÷ 1.3558179483314004, which works out to 73.756215 — matching the converter's actual output exactly.
A second example: a 20 Nm bolt spec in pound-inches, and pound-feet to pound-inches
A common bicycle stem-bolt torque spec of 20 Nm converts to 177.014916 lb·in using the pound-inch factor of 0.1129848290276167 N·m — the finer-grained unit torque wrenches use for smaller fasteners. Within the imperial units themselves, 1 lb·ft converts to exactly 12 lb·in, and running that 12 lb·in back through the converter to lb·ft returns exactly 1, confirming the pound-foot-to-pound-inch relationship is a clean 12x lever-arm scaling.
Why torque wrench specs still vary by manual
A single physical tightening spec ends up printed as three different-looking numbers — newton-meters in a metric manual, pound-feet in many US automotive references, and pound-inches for small-fastener work — purely because manufacturers target different regional conventions and fastener sizes. The converter's base-unit approach means all three numbers can be checked against each other instantly, without needing to memorize which factor applies to which pair.