Inch-Pound to Therm (EC)

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.

The EC therm is defined as exactly 105,505,600 joules; the US therm is 105,480,400 joules — a difference of 25,200 J (about 0.024%). The discrepancy arose from slightly different historical BTU definitions. For residential gas billing the difference is negligible, but in large-scale energy trading involving millions of therms, the distinction can affect settlement amounts.

The UK Gas Act 1995 mandated a switch from therms to kWh as part of broader metrication. One therm (EC) equals 29.3071 kWh. The change aligned gas billing with electricity billing, making it easier for consumers to compare energy costs. Older UK customers and industry veterans still refer to therms colloquially, and wholesale gas markets continued using therms for years after the retail switch.

A typical UK home uses 500–800 therms (EC) per year for heating and hot water, equivalent to roughly 14,700–23,400 kWh. Well-insulated newer homes may use under 400 therms, while large Victorian houses with poor insulation can exceed 1,200 therms. Ofgem's energy price cap is set in pence per kWh, but converting back to therms gives about £2.50–£3.50 per therm at recent rates.

One cubic meter of UK pipeline-quality natural gas contains roughly 38.5–39.5 MJ, which is about 0.365–0.374 therms (EC). Gas meters measure volume in cubic meters, and the utility applies a calorific value correction to convert to kWh (or therms). The correction factor varies by region and season because gas composition changes depending on the source field.

The therm (EC) was once the standard trading unit on the UK's NBP (National Balancing Point) gas market. In 2020, the ICE exchange switched NBP contracts from pence per therm to pence per kWh. Continental European hubs like TTF have always traded in euros per MWh. The therm is fading from professional use but remains in legacy contracts and older billing systems.