Unit Converters
Convert units quickly and accurately with free online unit converters. Instantly switch between length, weight, temperature, volume, and more.
Unit Calculators
Unit Converters
ToolsPiNG provides twelve free unit converters covering all major measurement categories: physical dimensions (length, weight, area, volume), conditions and rates (temperature, speed, pressure), energy and mechanics (power, torque), digital data (byte/bit), time, and electric charge. All converters run in your browser with no downloads, no sign-up, and instant results.
Each converter in this category goes beyond a simple unit list — individual tool pages cover the distinctions that matter in practice: which horsepower type applies to a European vs US engine, whether a pressure gauge reading is gauge or absolute, why a 1 TB hard drive shows as 931 GB in Windows, when to use troy vs avoirdupois ounces, and how Mach number varies with altitude.
Which converter do you need?
| What you need to convert | Tool | Key detail |
| Physical dimensions | ||
| Length — mm, cm, m, km, inches, feet, miles, nautical miles, and 23 more | Length Converter | 31 units including typography (pt, pica, em), astronomical (AU, light year, parsec), and scientific (angstrom, fermi). Three distinct nautical mile definitions. |
| Weight / mass — kg, lb, grams, ounces, troy oz, tons, carats | Weight Converter | 17 units across metric, avoirdupois, troy, and scientific systems. Includes all three ton definitions (short/long/metric) and both troy and avoirdupois ounces and pounds. |
| Area — m², ft², acres, hectares, km², square miles, and more | Area Converter | 13 units. Includes barn (nuclear physics), circular mil (US wire cross-section), rood, and are. Covers all major land area conversions. |
| Volume — liters, gallons, cups, pints, m³, barrels, and more | Volume Converter | 30 units — the largest unit set. Includes US liquid and US dry (different sizes), UK imperial, and industrial units (barrel, acre-foot, register ton, stere). |
| Conditions and rates | ||
| Temperature — Celsius, Fahrenheit, Kelvin, Rankine | Temperature Converter | 4 scales. All 6 direction formulas with worked examples. Oven temperature quick-reference table. Rankine explained (US aerospace/thermodynamics). -40 degrees is the same in both C and F. |
| Speed — km/h, mph, m/s, knots, Mach, ft/s, ft/min, and more | Speed Converter | 11 units. Mach number temperature-dependence explained (Mach 1 at altitude ≠ Mach 1 at sea level). Knots etymology and the 'knots per hour' error corrected. Speed scale reference table. |
| Pressure — PSI, bar, kPa, Pa, atm, Torr, mmHg, and more | Pressure Converter | 19 units. Gauge vs absolute pressure explained — the critical distinction for tire and compressor readings. Practical reference table (tire pressures, blood pressure, HVAC, hydraulics). |
| Energy, force, and power | ||
| Power — watts, kW, MW, horsepower (5 types), BTU/h | Power Converter | 20 units. Five distinct horsepower definitions (mechanical, metric PS/CV, electric, UK, boiler) — each with different watt values. BTU/h for HVAC. |
| Torque — N·m, ft-lb, in-lb, kgf·m | Torque Converter | 5 units. Includes torque vs power distinction, when to use each unit (N·m for European vehicles, ft-lb for US, in-lb for small fasteners), and bolt torque reference table. |
| Digital data and time | ||
| Digital storage and speed — bits, bytes, KB, MB, GB, TB, Mbps | Byte/Bit Converter | 14 units covering bits and bytes. Decimal (SI) vs binary (IEC) explained — why a 1 TB drive shows as ~931 GB in Windows. Mbps to MB/s download speed reference table. |
| Time duration — ms, seconds, minutes, hours, days, weeks, years, sidereal time | Time Converter | 23 units including sidereal time (astronomy/telescopes), three year definitions (calendar, tropical, sidereal), femtoseconds, shake, and fortnight. |
| Electric charge — coulombs, ampere-hours, faradays | Electric Charge Converter | 8 units: coulombs (SI), ampere-hours (battery capacity), Faraday system (electrochemistry), CGS legacy (abcoulomb, stat coulomb). Note: this is a charge converter, not a voltage converter. |
All 12 converters — what each covers
| Tool | What it covers and what makes it distinctive |
| Length Converter | 31 units. The most comprehensive length converter in this suite. Covers all common metric and imperial units plus 3 nautical mile definitions, typography units (pt, pica, em), scientific units (angstrom, fermi), and astronomical units (AU, light year, parsec). Includes a warning on mil vs millimeter confusion (they differ by 40x). |
| Weight Converter | 17 units. Clearly separates avoirdupois (everyday), troy (precious metals), and metric. The troy ounce vs avoirdupois ounce distinction is critical — troy is 9.7% heavier and used for all gold/silver pricing. All three ton definitions (short/long/metric) with the ~10% discrepancy table. |
| Temperature Converter | 4 scales. All 6 conversion formulas with worked examples. Includes Rankine (US aerospace). Oven temperature quick-reference table for cooking conversions. Key insight: -40°C = -40°F, the only temperature that is the same on both scales. |
| Area Converter | 13 units. Unusual units explained: barn (10^-28 m², nuclear physics), circular mil (US wire cross-section, NEC vs IEC standards), rood (quarter acre, historic UK land deeds), and are (100 m², source of 'hectare'). Land size comparison table from studio apartment to 1 square mile. |
| Volume Converter | 30 units — most in the category. US liquid vs US dry distinction (same names, different sizes), UK vs US gallon (20% difference), cooking quick-reference table. Industrial units: oil barrel (42 US gallons), acre-foot (water management), register ton (ship cargo volume), stere (firewood). |
| Speed Converter | 11 units. Mach number varies with temperature — Mach 1 at sea level (1,225 km/h) differs from Mach 1 at altitude (1,062 km/h). Knots history (knotted rope / sandglass). Speed scale reference from walking pace to SR-71. |
| Pressure Converter | 19 units. Gauge pressure vs absolute pressure — the most important distinction (tire gauges show gauge; scientific specs use absolute). Practical reference table for tire pressures, blood pressure, HVAC, scuba, and hydraulics. PSI to bar quick conversions. |
| Power Converter | 20 units. Five distinct horsepower types with different watt values: mechanical (745.7 W), metric PS/CV (735.5 W), electric (746 W), UK (745.7 W), boiler (9,810 W). Power vs energy distinction — watts measure rate, watt-hours measure total. |
| Torque Converter | 5 units. Torque formula (force × arm length) explained. Torque vs power distinction with the formula. Unit guide: N·m for European vehicles, ft-lb for US, in-lb for small fasteners, kgf·m for vintage Japanese/European manuals. Bolt torque reference table for automotive work. |
| Byte/Bit Converter | 14 units. The two biggest confusions in computing: bits vs bytes (divide Mbps by 8 for MB/s) and decimal vs binary (1 TB = 1,000,000,000,000 bytes = ~931 GiB — why Windows shows less than the labelled capacity). Download speed reference table. |
| Time Converter | 23 units. Sidereal time (for telescopes — ~4 min/day shorter than solar), three year types (calendar, tropical, sidereal — use calendar year = 31,536,000 s for software), shake (10 ns, nuclear physics), fortnight (2 weeks, UK/Australian payroll). |
| Electric Charge Converter | 8 units. Converts electric charge — coulombs, ampere-hours, faradays. Not a voltage converter despite the page name. Battery capacity (mAh to coulombs: multiply by 3.6), Faraday unit (96,485 C per mole of electrons — electrochemistry). Faraday vs farad distinction. |
Common multi-converter workflows
Several practical tasks require more than one converter. The table below shows common scenarios where two converters work together:
| Task | Tools used | Workflow |
| Calculate vehicle fuel economy across UK / US units | Length + Volume | Convert miles to km using Length Converter. Convert UK gallons to US gallons (or litres) using Volume Converter. Calculate fuel economy in both systems. Note: UK mpg and US mpg use different gallon sizes — a car at 40 mpg (UK) = approximately 33 mpg (US). |
| Convert a recipe from US cups to metric grams | Volume + Weight | Convert US cups to ml using Volume Converter (1 US cup = 236.6 mL; Australian/metric cup = 250 mL). For ingredients where weight matters more than volume (flour, sugar), use the Weight Converter. Density is required to convert volume to weight — 1 cup of flour ≈ 120–130 g depending on how packed it is. |
| Calculate broadband speed for a file download | Byte/Bit Converter | Take your broadband speed in Mbps. Divide by 8 to get MB/s (the Byte/Bit Converter confirms this — 1 byte = 8 bits). Example: 200 Mbps / 8 = 25 MB/s. A 4 GB file takes 4,000 MB / 25 MB/s = 160 seconds. |
| Convert engine torque and power from US to European specs | Torque + Power | Engine torque: use Torque Converter — lbf·ft to N·m (multiply by 1.356). Engine power: use Power Converter — hp (mechanical) to kW (multiply by 0.7457). Example: 300 lb·ft / 250 hp = 406.8 N·m / 186.4 kW. |
| Set tyre pressure when abroad | Pressure Converter | Your manual may state PSI, but European pumps show bar, Australian pumps show kPa. Use the Pressure Converter. Typical passenger car: 32–36 PSI = 2.2–2.5 bar = 220–250 kPa. Remember: your vehicle's sticker shows the recommended gauge pressure for cold tires. |
Key distinctions to know across the category
Metric vs imperial — which system uses what
The United States primarily uses US customary units (miles, pounds, Fahrenheit, gallons, PSI, ft-lb). The UK uses a mix — metric for most purposes but miles for road distances, pints for draught beer, and stone/pounds for body weight. All other countries use the metric SI system. In engineering and science, SI units are used internationally regardless of country. When a specification could be in either system — an automotive service manual, a recipe, a land description — always check the document's origin country before converting.
The same name, different values — the most common conversion traps
- Gallon: US liquid gallon (3.785 L) vs UK imperial gallon (4.546 L) — 20% difference.
- Pint: US liquid pint (473 mL) vs UK pint (568 mL) vs US dry pint (551 mL) — three different values.
- Ounce: avoirdupois fluid ounce (29.6 mL) vs UK fluid ounce (28.4 mL) vs troy ounce (31.1 g — mass, not volume).
- Ton: US short ton (907 kg) vs UK long ton (1,016 kg) vs metric ton (1,000 kg).
- Horsepower: mechanical (745.7 W) vs metric PS/CV (735.5 W) vs electric (746 W exactly) vs boiler (9,810 W).
- Mach: Mach 1 at sea level = 1,225 km/h; Mach 1 at 35,000 ft = 1,062 km/h.
Gauge vs absolute pressure
Tyre gauges, compressor gauges, and most everyday pressure instruments display gauge pressure — measured relative to the current atmospheric pressure. Absolute pressure is measured from a perfect vacuum. A tyre at 35 PSI gauge pressure has an absolute pressure of approximately 49.7 PSI. For comparing tyre pressures between PSI and bar, no correction is needed — gauge readings convert directly. Problems arise when mixing gauge instrument readings with absolute specifications.
Bits vs bytes in digital conversion
File sizes are measured in bytes (KB, MB, GB). Network speeds are measured in bits per second (Kbps, Mbps, Gbps). Capital B = bytes; lowercase b = bits. 1 byte = 8 bits. To find the download speed of a file in MB/s from an Mbps connection speed: divide by 8. A 100 Mbps connection downloads at 12.5 MB/s.
Usage limits
| Account type | Daily limit | Applies to |
| Guest | 25 per day | Each tool independently — 25 conversions per tool per day |
| Registered | 100 per day | Each tool independently — 100 conversions per tool per day |
Frequently asked questions
Do I need to download or install anything to use these converters?
No. All 12 converters run entirely in your browser using standard web technology. No account is required, no software needs to be installed, and no data is stored. Guest users can perform 25 conversions per tool per day; registering a free ToolsPiNG account increases this to 100 per tool per day.
Which converter should I use for cooking recipe conversions?
Use the Volume Converter for liquid measurements (cups, tablespoons, fluid ounces, liters, milliliters) and the Weight Converter for ingredient amounts stated by mass (grams, ounces, pounds). The Volume Converter includes a cooking quick-reference table. Important: the metric cup (250 mL, used in Australia and Canada) differs from the US cup (236.6 mL) — for precise baking, use exact mL values rather than assuming cups are interchangeable. The UK tablespoon (20 mL) also differs significantly from the US tablespoon (14.8 mL).
Which converter should I use for tire pressure?
Use the Pressure Converter. Select the unit your vehicle manual specifies (PSI, bar, or kPa) and convert to the unit shown on the pump. Common equivalents: 32 PSI ≈ 2.2 bar ≈ 220 kPa; 35 PSI ≈ 2.4 bar ≈ 240 kPa. Your vehicle's correct pressure is on the door-jamb sticker (driver's door frame), not on the tire sidewall — the sidewall shows the maximum, not the recommended, pressure.
Why does my 1 TB hard drive show as less than 1 TB in Windows?
Hard drive manufacturers use decimal definitions: 1 TB = 1,000,000,000,000 bytes. Windows displays storage in binary units: 1 TiB = 1,099,511,627,776 bytes. So 1,000,000,000,000 bytes / 1,099,511,627,776 = approximately 0.909 TiB, displayed as '909 GB'. Neither is wrong — they use different definitions of the prefix. The Byte/Bit Converter explains both systems and includes a conversion table for comparing decimal (SI) and binary (IEC) sizes.
What is the difference between a US gallon and a UK gallon?
The US liquid gallon = 3.785 liters. The UK (Imperial) gallon = 4.546 liters. The UK gallon is approximately 20% larger. This affects fuel economy comparisons: a car achieving 40 mpg (UK) achieves approximately 33 mpg (US). The Volume Converter separates all US liquid, US dry, and UK imperial gallon definitions. Always check which gallon definition a specification uses before converting.
Which horsepower type should I use for vehicle comparisons?
For US-market vehicles: mechanical horsepower (745.7 W each). For European-market vehicles: check whether the spec uses kW or metric PS/CV (735.5 W each) — both are common. For direct cross-market comparison, convert both values to kilowatts using the Power Converter with the appropriate horsepower type selected. A US car at 200 hp (mechanical) = 149.1 kW; a European car at 200 PS = 147.1 kW — a 1.4% difference that matters for precise comparisons.
Is the Electric Charge Converter a voltage converter?
Despite the page name, the Electric Charge Converter converts units of electric charge — coulombs, ampere-hours, faradays, and CGS units — not voltage (volts, millivolts, kilovolts). Voltage is measured in volts; electric charge is measured in coulombs. The most practical use is battery capacity conversion: 1 ampere-hour = 3,600 coulombs; a 3,000 mAh smartphone battery = 3 Ah = 10,800 coulombs. If you need to convert voltage unit prefixes (mV to V, V to kV), these are simple powers of 10: 1 V = 1,000 mV; 1 kV = 1,000 V.