Grams of TNT to Inch-Pound

By convention, exactly 4,184 joules — the same as one thermochemical kilocalorie. Real TNT detonation yields vary by about ±2% depending on purity and confinement, but the defined value provides a fixed reference point. This makes the gram of TNT a convenient bridge between chemistry (calories) and explosive engineering.

TNT (trinitrotoluene) became the reference explosive because it is chemically stable, safe to handle, and was massively produced during both World Wars. Its consistent detonation properties made it a natural benchmark. Other explosives are rated by their "TNT equivalent" — for example, C-4 is about 1.34× TNT and ANFO is about 0.74× TNT.

A standard US consumer firecracker contains about 0.5–1 gram of TNT equivalent in flash powder. An M-80 (now illegal for consumer sale) contained roughly 3 g of TNT equivalent. Cherry bombs were about 1.5 g. Commercially sold fireworks are regulated by the CPSC to contain no more than 50 mg of flash powder per report charge.

A US M67 fragmentation grenade contains about 180 g of Composition B explosive, which has a TNT equivalence of about 1.33×, giving roughly 240 grams of TNT equivalent. The lethal radius is about 5 meters, with a casualty-producing radius of 15 meters. The fragmentation — not the blast energy alone — is the primary wounding mechanism.

One gram of TNT releases exactly 1 thermochemical kilocalorie (1 kcal = 4,184 J) by definition. This means a dietary Calorie (nutritional kcal) contains the same energy as detonating one gram of TNT. A 2,000-Calorie daily diet is energetically equivalent to 2 kg of TNT — though your body releases that energy over 24 hours, not in microseconds.

Inch-pounds provide finer resolution for small fasteners where foot-pound values would be fractions (e.g., 3 in·lb vs 0.25 ft·lb). Electronics assembly, firearms scope mounting, and bicycle component installation all specify inch-pounds because over-torquing a small screw by even one foot-pound can strip threads or crack housings.

On an M3 screw into aluminum (spec: 5 in·lb), exceeding by 2 in·lb — a 40% overload — can strip the threads or crack a thin boss. Small fasteners have almost no safety margin because the thread engagement area is tiny and the materials (plastic, aluminum, brass) are soft. This is why electronics repair shops use beam-type or preset click torque drivers accurate to ±0.5 in·lb, and why aerospace assembly procedures treat inch-pound specs as hard limits, not suggestions.

Laptop hinge screws typically require 2–5 in·lb, hard drive mounting screws 2–4 in·lb, and motherboard standoff screws 5–8 in·lb. Going beyond the spec risks cracking plastic bosses or stripping soft aluminum threads. A precision bit driver with a torque limiter is essential for electronics repair work.

Dimensionally they are identical — force times distance — but context differs. As torque, 1 in·lb means one pound-force applied at one inch from a pivot. As energy, it means one pound-force pushing through one inch of linear displacement (0.11299 J). In practice, inch-pounds almost always refer to torque in mechanical specifications.

Scope rings and bases use small screws that are easily damaged, and consistent clamping force is critical for zero retention under recoil. Typical specs are 15–25 in·lb for ring screws and 30–65 in·lb for base screws. Under-torquing lets the scope shift; over-torquing cracks the scope tube or strips the screw. A dedicated inch-pound torque wrench is considered essential kit for precision rifle setup.