Watt Hour to Inch-Ounce
Wh
in-oz
Conversion History
| Conversion | Reuse | Delete |
|---|---|---|
| No conversion history to show. | ||
Quick Reference Table (Watt Hour to Inch-Ounce)
| Watt Hour (Wh) | Inch-Ounce (in-oz) |
|---|---|
| 1 | 509,802.9575804458736581669 |
| 5 | 2,549,014.78790222936829083449 |
| 10 | 5,098,029.57580445873658166898 |
| 20 | 10,196,059.15160891747316333796 |
| 50 | 25,490,147.87902229368290834489 |
| 100 | 50,980,295.75804458736581668978 |
| 500 | 254,901,478.79022293682908344892 |
About Watt Hour (Wh)
A watt-hour (Wh) is the energy consumed or produced by a one-watt device operating for one hour, equal to 3,600 joules. It is widely used for small battery and energy storage capacities — smartphone batteries, power banks, and small electronic devices. A smartphone battery holds roughly 10–15 Wh; a laptop 50–100 Wh. The watt-hour is the stepping-stone unit between the joule (too small for practical appliance use) and the kilowatt-hour (the billing unit for mains electricity).
A phone charger running for an hour uses about 5–10 Wh. A 100 Wh portable power bank can charge a typical smartphone about seven times.
About Inch-Ounce (in-oz)
The inch-ounce (in·oz) is a unit of very small torque equal to approximately 0.007062 joules — 1/16 of an inch-pound. It is used for servo motor torque ratings in model aircraft and small robotics, miniature instrument spring tensions, and the adjustment of precision optical and scientific instruments. Where inch-pounds are too coarse for the application, inch-ounces provide a finer unit without switching to SI.
A small servo motor for a model aircraft may be rated at 40–80 in·oz of torque. A clock escapement spring tension is typically a few in·oz.
Watt Hour – Frequently Asked Questions
Why are portable battery capacities listed in watt-hours instead of milliamp-hours?
Watt-hours account for both current and voltage, giving the true energy stored. A 10,000 mAh power bank at 3.7 V holds 37 Wh, but at 5 V output it delivers only about 7,400 mAh due to voltage conversion losses. Airlines use the Wh rating (max 100 Wh carry-on) because it reflects actual energy — and therefore actual fire risk — regardless of battery voltage.
How many watt-hours does a typical smartphone battery hold?
Most smartphones have batteries rated at 10–18 Wh. An iPhone 15 Pro holds about 12.7 Wh; a Samsung Galaxy S24 Ultra about 18.4 Wh. For context, fully charging an 18 Wh phone from a wall outlet costs less than 0.01 kWh — roughly one-tenth of a cent on a typical electricity bill.
What is the airline limit for lithium batteries in watt-hours?
Most airlines allow lithium-ion batteries up to 100 Wh in carry-on luggage without approval. Batteries between 100 and 160 Wh (e.g., large camera or drone batteries) require airline permission, and batteries above 160 Wh are banned from passenger flights. A standard laptop battery is 50–100 Wh; a large power tool battery can exceed 160 Wh.
Why did the electronics industry settle on watt-hours instead of joules for battery labels?
Watt-hours map directly to how consumers think about devices: a 50 Wh battery powering a 10 W laptop lasts about 5 hours — simple division. Expressing the same battery as 180,000 joules gives no intuitive sense of runtime. Airlines also adopted Wh for lithium battery safety limits (100 Wh carry-on threshold) because it communicates energy density risk in a unit engineers and passengers can both grasp.
How many watt-hours does it cost to charge a laptop?
A typical laptop battery holds 50–100 Wh, so a full charge from empty uses 50–100 Wh of energy (plus about 10–15% lost as heat in the charger). At average US electricity rates, that is roughly 1–2 cents per charge. Over a year of daily charging, a laptop costs about $4–$7 in electricity — far less than most people assume.
Inch-Ounce – Frequently Asked Questions
What are inch-ounces used for in hobby servos and RC models?
RC servo motors are rated by torque in inch-ounces (or oz·in) because the forces involved are tiny. A standard micro servo produces 40–60 in·oz, which is enough to deflect a model aircraft aileron. High-torque digital servos for 1/10-scale RC cars reach 200–400 in·oz. The inch-ounce scale gives hobbyists whole-number specs that are easy to compare.
Why do high-end RC servos specify torque at different voltages (4.8V vs 6V)?
Servo motors produce more torque at higher voltage because the motor windings draw more current and generate a stronger magnetic field. A servo rated at 60 in·oz at 4.8 V might deliver 75 in·oz at 6 V — a 25% boost. RC pilots choose voltage based on the tradeoff: 6 V gives snappier response and more holding torque for aerobatics, but draws more current and generates more heat, reducing servo lifespan. Competition flyers often run 7.4 V for maximum performance, accepting shorter gear life.
Why use inch-ounces instead of newton-meters for small torque values?
Inch-ounces give convenient whole numbers for very small torques where newton-meters would be awkward decimals (e.g., 50 in·oz ≈ 0.353 N·m). The RC hobby, miniature clockwork, and precision instrument industries in the US developed around imperial units, and the convention persists even as SI gains ground. Many datasheets now list both units side by side.
What torque in inch-ounces does a clock or watch mechanism require?
A mechanical wristwatch mainspring delivers roughly 2–5 in·oz of torque. Larger mantel clocks may have mainspring torques of 10–30 in·oz. Escapement adjustments are even finer, sometimes below 1 in·oz. Horologists use inch-ounces (or gram-centimeters) because these scales match the delicate forces in timekeeping mechanisms.
How does inch-ounce torque relate to servo motor performance in robotics?
A servo's inch-ounce rating tells you the maximum force it can exert at one inch from the output shaft. A 100 in·oz servo can hold 100 ounces (6.25 lb) at 1 inch, or 50 ounces at 2 inches. Robotics designers use this to size servos for joint loads — a small robotic arm lifting 1 lb at 4 inches needs at least 64 in·oz, plus a safety margin of 50% or more.