What’s gauge pressure vs absolute pressure?

Gauge (psig, barg) excludes atmospheric pressure; absolute (psia, bara) includes it. To convert, add or subtract local atmospheric pressure (~101.325 kPa at sea level).

Unit Converters — Fast, Accurate Conversions (Free)

Q: What’s the most reliable way to convert units?

Use the SI base-unit method: convert the input to a base unit (e.g., meters), then from the base unit to your target. This avoids chained rounding errors.

Q: What’s the difference between kB and KiB?

kB (decimal) = 1,000 bytes; KiB (binary) = 1,024 bytes. For storage manufacturers use decimal; for operating systems and memory, binary is common.

Q: How do I convert Celsius to Fahrenheit and Kelvin?

°F = (°C × 9/5) + 32; K = °C + 273.15. Remember Kelvin is absolute temperature and has no degree symbol.

Q: How many significant figures should I keep?

Match the precision of your least certain input. For most everyday uses 2–4 significant figures are reasonable; show more when engineering requires it.

Q: Can I mix metric and imperial units?

Yes. All converters support metric and imperial. You can enter either and select the desired output system.

Q: Why don’t my conversions match a handbook exactly?

Reference tables sometimes use rounded factors or different standards (e.g., °F vs Rankine). Our tools use high-precision factors; small differences come from rounding.

Q: How do I convert horsepower to kilowatts?

1 mechanical horsepower (hp) = 0.745699872 kW. Multiply hp by 0.745699872 to get kW, or use the Power Converter.

Q: Is currency conversion live?

The Simple Currency Converter uses the rate you provide (or a preset if available). For trading or taxes, confirm rates with your bank or a live source.

Q: Where are time zone or epoch converters?

See the Time & Date hub for time zone and epoch tools. This hub focuses on physical and computing units.

Who this hub is for

Students, engineers, makers, and anyone who needs clean, trustworthy conversions. Use the featured cards, compare table and worked examples to jump straight to the right converter.

Note: Conversions are mathematical transforms. For code-compliance, lab work or procurement, follow your applicable standards and required rounding rules.

Best Unit Converters (Quick Picks)

All-in-One Converter

One panel for many units—handy when you’re in a rush.

Open

Temperature

Convert °C, °F and K with exact formulas.

Open

Power

kW ↔ hp, W, dBm and more—precision factors.

Open

Data Size & Rate

Bytes vs bits, decimal vs binary (KB vs KiB).

Open Size Open Rate

Compare Tools

Tool	Best For	Inputs	Outputs
All-in-One	Quick multi-unit checks	Value + category	Common targets	Open
Length	Civil & machining	m, mm, in, ft…	Any length unit	Open
Mass	Lab & logistics	kg, g, lb, oz…	Any mass unit	Open
Volume	Fluids & batching	L, mL, m³, gal…	Any volume unit	Open
Area	Flooring & land	m², ft², ha, ac…	Any area unit	Open
Speed	Vehicles & flow	m/s, km/h, mph…	Any speed unit	Open
Pressure	HVAC & process	Pa, bar, psi…	Any pressure unit	Open
Energy & Power	Electrical & engines	J, kWh, W, hp…	J↔kWh, W↔hp…	Energy · Power
Temperature	Science & cooking	°C, °F, K	Exact conversions	Open
Data Size / Rate	Networking & storage	B, b, KB/KiB…; bps	Decimal & binary	Size · Rate
Density / Viscosity	Fluids & materials	kg/m³, cP, Pa·s…	Any target unit	Density · Viscosity
Electric Units	Circuits & power	V, A, Ω, W…	Derived values	Open
Scientific Notation	Lab & formatting	Number & exponent	Decimal ↔ sci-notation	Open

Core SI & Mechanics

Fluids, Materials & Light

Density, Viscosity, Flow-Rate
Angle, Luminous, Radiation

Computing & Signals

Other Helpful Converters

Time Unit Converter — seconds, minutes, hours, days.
Simple Currency — enter your rate (finance tools link below).

Worked Examples

Vehicle speed: 27.8 m/s → ? km/h. Enter 27.8 in Speed to see 100 km/h (exact).
Shop motor rating: 2.5 hp → kW. In Power, 2.5 hp ≈ 1.864 kW (mechanical hp × 0.745699872).
Storage label vs OS: 10 “GB” (decimal) vs GiB (binary). In Storage, 10 GB ≈ 9.313 GiB.
Pressure units: 2.3 bar → psi. In Pressure, 2.3 bar ≈ 33.36 psi.

Frequently Asked Questions

What’s the most reliable way to convert units?

Use the SI base-unit method: convert to base (e.g., meters), then to your target. It prevents chained rounding drift.

What’s the difference between kB and KiB?

kB = 1000 bytes; KiB = 1024 bytes. Decimal vs binary prefixes.

How do I convert Celsius to Fahrenheit and Kelvin?

°F = (°C × 9/5) + 32; K = °C + 273.15.

How many significant figures should I keep?

Match the least certain input—usually 2–4 sig figs for general use.

Can I mix metric and imperial units?

Yes—enter either; choose the desired output system.

Why don’t my conversions match a handbook exactly?

Different references round differently or use alternate standards. We use high-precision factors.

How do I convert horsepower to kilowatts?

hp × 0.745699872 = kW. Try the Power Converter for instant results.

What’s gauge vs absolute pressure?

Gauge excludes atmospheric pressure; absolute includes it. Convert by adding/subtracting local atmospheric pressure.

Is currency conversion live?

Our Simple Currency converter uses the rate you enter (or a preset). Confirm live rates with your bank for financial decisions.

Where are time zone or epoch converters?

They live in the Time & Date hub.

Converters Disclaimer

Results are based on standard conversion factors and exact formulas where applicable. For regulated work (engineering drawings, compliance, procurement), use required standards and rounding rules for your jurisdiction.

Precision: Keep significant figures consistent with your source data.
Standards: Be mindful of decimal vs binary prefixes and local measurement standards.
No warranty: Outputs are provided “as is.” Verify before critical use.

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Last updated: September 17, 2025

How to Convert Like a Pro (SI method)

The safest way to convert is to go through the SI base unit. Example: km/h → m/s.

1) Convert to base:
   90 km/h × (1000 m / 1 km) × (1 h / 3600 s) = 25 m/s
2) Convert to target (if needed):
   25 m/s × (3.6 km/h per m/s) = 90 km/h (check)

Advantages: fewer steps, fewer rounding issues, and a mental model that works across categories.

Handy Factors

1 in = 25.4 mm (exact)
1 hp = 0.745699872 kW
1 bar = 100,000 Pa
1 L  = 0.001 m³
KB vs KiB: 1 KB = 1000 B; 1 KiB = 1024 B

Popular Use Cases

Machining drawings: inch ↔ mm with exact 25.4 mm/in.
Networking: Mb/s ↔ MB/s when sizing transfers.
HVAC: Pa ↔ inH₂O for duct static pressure.
Chemistry: cP ↔ mPa·s for viscosity specs.

Who this hub is for

Best Unit Converters (Quick Picks)

All-in-One Converter

Temperature

Power

Data Size & Rate

Compare Tools

Core SI & Mechanics

Fluids, Materials & Light

Computing & Signals

Other Helpful Converters

Worked Examples

Frequently Asked Questions

Converters Disclaimer

Related Hubs

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