Online utility calculators and tools

Practical tools for everyday use: unit converters (length, area, volume, mass, temperature, speed, pressure, energy and density), a PDF editor, a QR code generator and calculators for power banks and solar panels. Pick a tool from the menu on the left or from the cards below; conversion factors, notes and frequently asked questions are further down.

Featured tools

ConverterLength converterConversion between length units. SI reference: meter (m). ToolQR code generatorGenerate QR codes. ToolPDF editorEdit PDF files directly online.

Unit converters

Nine converters for the most common quantities. Choose the quantity: the tool opens at the top of this page.

ConverterLengthConversion between length units. SI reference: meter (m). ConverterAreaConversion between area units. SI reference: square meter (m²). ConverterVolumeConversion between volume units. SI reference: cubic meter (m³). ConverterMassConversion between mass units. SI reference: kilogram (kg). ConverterTemperatureConversion between temperature scales. SI reference: kelvin (K). ConverterSpeedConversion between speed units. SI reference: meter per second (m/s). ConverterPressureConversion between pressure units. SI reference: pascal (Pa). ConverterEnergyConversion between energy units. SI reference: joule (J). ConverterDensityConversion between density units. SI reference: kg/m³.

PDF editor and QR codes

ToolPDF editorEdit PDF files directly online. ToolQR code generatorGenerate QR codes.

Power banks and solar panels

CalculatorPower bank calculatorCalculate the runtime of a power bank. CalculatorSolar panel calculatorCalculate the runtime with solar panels.

Conversion factors

To convert a measurement you only need the value of each unit in SI units. These are the reference factors for the most used units.

QuantityUnitValue in SI units
Lengthinch0.0254 m
Lengthfoot0.3048 m
Lengthyard0.9144 m
Lengthmile1,609.344 m
Lengthnautical mile1,852 m
Areaacre4,046.8564224 m²
VolumeUS gallon3.785411784 L
Masspound0.45359237 kg
Massounce0.028349523125 kg
Speedmile per hour (mph)0.44704 m/s
Speedknot1,852 / 3,600 m/s ≈ 0.5144 m/s
Pressureatmosphere101,325 Pa
Pressurepsi≈ 6,894.757 Pa
Energykilowatt-hour (kWh)3.6 MJ

Reference conversion factors to SI units.

Practical notes

To convert a value from unit A to unit B, use xB = xA · fA / fB, where f is the value of each unit in SI units. Example: 5 miles in kilometers, with f = 1,609.344 m for the mile and 1,000 m for the kilometer, give 5 · 1,609.344 / 1,000 = 8.04672 km. Temperatures are an exception, because the scales have different zeros: °F = °C · 9/5 + 32 and K = °C + 273.15.

Frequently asked questions

How do you convert units of measurement?

You go from the starting unit to the SI unit and then to the target unit, with xB = xA · fA / fB. Example: 2.5 inches are 2.5 · 0.0254 = 0.0635 m, that is 6.35 cm.

How do you convert Fahrenheit to Celsius?

°C = (°F − 32) · 5/9. Example: 100 °F corresponds to (100 − 32) · 5/9 ≈ 37.78 °C. To go from Celsius to kelvin, add 273.15.

How many square meters are in an acre?

One acre equals 4,046.8564224 m², about 0.4047 hectares.

How do you calculate the energy of a power bank?

In general, the energy in watt-hours is the capacity in mAh times the nominal voltage in volts, divided by 1,000: 10,000 mAh at 3.7 V is 37 Wh. Some energy is lost in conversion, so the usable energy is lower.