Tons of TNT to Inch-Pound

One ton of TNT releases 4.184 GJ — roughly the energy of 120 liters of petrol or the electricity an average US home uses in 1.2 days. In blast terms, one ton of TNT in open air produces lethal overpressure within about 15–20 meters and can shatter windows at 100+ meters. The MOAB bomb (11 tons TNT) flattened structures across a 150-meter radius.

They differ by factors of 1,000: 1 kiloton = 1,000 tons, 1 megaton = 1,000,000 tons. Conventional bombs are rated in tons (the MOAB is 11 tons). Tactical nuclear weapons are rated in kilotons (Hiroshima was ~15 kt). Strategic thermonuclear warheads are rated in megatons (modern US warheads are 0.3–0.475 Mt). The scale spans nine orders of magnitude.

The 2020 Beirut explosion was caused by 2,750 tonnes of ammonium nitrate and was estimated at roughly 500–1,100 tons of TNT equivalent. For comparison, the Oklahoma City bombing (1995) was about 2 tons TNT equivalent, and the Halifax explosion (1917) was roughly 2,900 tons. Beirut ranked among the largest non-nuclear explosions in history.

Small meteor airbursts are rated in tons or kilotons of TNT. The 2013 Chelyabinsk meteor released about 440,000 tons (440 kt) — roughly 30 times the Hiroshima bomb. The Tunguska event (1908) is estimated at 3–15 megatons. The Chicxulub asteroid that ended the dinosaurs released roughly 100 trillion tons (100 million megatons) of TNT equivalent energy.

The largest planned non-nuclear explosion was the British demolition of Heligoland fortifications in 1947, using 6,700 tons of TNT equivalent. The largest accidental explosion was the Halifax harbour disaster (1917) at roughly 2,900 tons. The largest conventional bomb, the US GBU-43/B MOAB, yields about 11 tons — tiny compared to accidental industrial blasts.

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.