1. SI base units
| Quantity | SI unit | Symbol |
|---|---|---|
| Length | metre / meter | m |
| Mass | kilogram | kg |
| Time | second | s |
| Electric current | ampere | A |
| Thermodynamic temperature | kelvin | K |
| Amount of substance | mole | mol |
| Luminous intensity | candela | cd |
This page contains a basic overview of the most common unit conversions. It is based on SI units and several practical additional units used in everyday life, technology and aviation.
The values are intended for quick reference. For professional calculations, it is advisable to verify the exact definition of the unit and use the appropriate number of significant figures.
2. SI prefixes
| Prefix | Symbol | Factor |
|---|---|---|
| tera | T | 10¹² |
| giga | G | 10⁹ |
| mega | M | 10⁶ |
| kilo | k | 10³ |
| hecto | h | 10² |
| deca | da | 10¹ |
| deci | d | 10⁻¹ |
| centi | c | 10⁻² |
| milli | m | 10⁻³ |
| micro | µ | 10⁻⁶ |
| nano | n | 10⁻⁹ |
| pico | p | 10⁻¹² |
3. Large numbers – Czech and English naming
Czech commonly uses the long scale. Modern English usually uses the short scale, so special care is needed with the words billion and trillion.
| Number | Czech name | Usual English name | Note |
|---|---|---|---|
| 10⁶ | milion | million | The same meaning. |
| 10⁹ | miliarda | billion | English billion is not Czech bilion. |
| 10¹² | bilion | trillion | Czech bilion = English trillion. |
| 10¹⁵ | biliarda | quadrillion | Different naming system. |
| 10¹⁸ | trilion | quintillion | Different naming system. |
4. Length
| Unit | Conversion |
|---|---|
| 1 km | 1,000 m |
| 1 m | 100 cm |
| 1 cm | 10 mm |
| 1 inch | 25.4 mm |
| 1 foot | 0.3048 m |
| 1 yard | 0.9144 m |
| 1 mile | 1.609344 km |
| 1 nautical mile / NM | 1,852 m |
5. Area
| Unit | Conversion |
|---|---|
| 1 m² | 10,000 cm² |
| 1 are | 100 m² |
| 1 hectare | 10,000 m² |
| 1 km² | 1,000,000 m² |
| 1 acre | approximately 4,046.86 m² |
6. Volume
| Unit | Conversion |
|---|---|
| 1 m³ | 1,000 l |
| 1 l | 1 dm³ |
| 1 ml | 1 cm³ |
| 1 hl | 100 l |
| 1 US gallon / US gal | approximately 3.785 l |
| 1 imperial gallon / imp gal | approximately 4.546 l |
7. Mass
| Unit | Conversion |
|---|---|
| 1 t | 1,000 kg |
| 1 kg | 1,000 g |
| 1 g | 1,000 mg |
| 1 pound / lb | 0.453592 kg |
| 1 ounce / oz | approximately 28.3495 g |
8. Time
| Unit | Conversion |
|---|---|
| 1 min | 60 s |
| 1 h | 3,600 s |
| 1 day | 24 h = 86,400 s |
| 1 week | 7 days |
| 1 year | 365 days, leap year 366 days |
9. Speed
| Unit | Conversion |
|---|---|
| 1 m/s | 3.6 km/h |
| 1 km/h | 0.27778 m/s |
| 1 knot / kt | 1.852 km/h |
| 1 mph | 1.609344 km/h |
| 1 Mach | approximately 1,225 km/h at 15 °C at sea level |
10. Temperature
| Conversion | Formula |
|---|---|
| °C to K | K = °C + 273.15 |
| K to °C | °C = K − 273.15 |
| °C to °F | °F = °C × 9/5 + 32 |
| °F to °C | °C = (°F − 32) × 5/9 |
11. Pressure
| Unit | Conversion |
|---|---|
| 1 Pa | 1 N/m² |
| 1 kPa | 1,000 Pa |
| 1 hPa | 100 Pa |
| 1 bar | 100,000 Pa |
| 1 atm | 101,325 Pa |
| 1 psi | approximately 6,894.76 Pa |
| 1 mmHg | approximately 133.322 Pa |
12. Force
| Unit | Conversion / meaning |
|---|---|
| 1 N | the force that gives a mass of 1 kg an acceleration of 1 m/s² |
| 1 kN | 1,000 N |
| 1 kgf / kilopond | approximately 9.80665 N |
| 1 lbf | approximately 4.44822 N |
13. Work and energy
In physics, work and energy have the same unit – the joule. Mechanical work is force acting over a distance.
| Unit | Conversion / meaning |
|---|---|
| 1 J | 1 N·m = 1 W·s |
| 1 kJ | 1,000 J |
| 1 MJ | 1,000,000 J |
| 1 Wh | 3,600 J |
| 1 kWh | 3.6 MJ |
| 1 kcal | approximately 4.184 kJ |
14. Power
| Unit | Conversion / meaning |
|---|---|
| 1 W | 1 J/s |
| 1 kW | 1,000 W |
| 1 MW | 1,000,000 W |
| 1 hp / horsepower | approximately 735.5 W |
15. Electrical quantities
| Quantity / unit | Meaning |
|---|---|
| 1 A | ampere, unit of electric current |
| 1 V | volt, unit of electric voltage |
| 1 Ω | ohm, unit of electrical resistance |
| 1 W | watt, unit of electric power |
| 1 Ah | ampere-hour, often used for batteries |
| 1 kWh | kilowatt-hour, a common unit of electricity consumption |
16. Frequency and rotational speed
| Unit | Conversion / meaning |
|---|---|
| 1 Hz | 1 cycle per second |
| 1 kHz | 1,000 Hz |
| 1 MHz | 1,000,000 Hz |
| 1 rpm | 1 revolution per minute |
| 60 rpm | 1 rev/s = 1 Hz |
17. Practical aviation units
| Unit | Conversion | Use |
|---|---|---|
| 1 ft | 0.3048 m | Height / altitude in aviation. |
| 1,000 ft | 304.8 m | Approximate conversion of flight altitudes. |
| 1 NM | 1.852 km | Nautical and aviation distance. |
| 1 kt | 1.852 km/h | Speed in aviation and maritime navigation. |
| 1 m/s | approximately 196.85 ft/min | Climb or descent rate. |
| 100 ft/min | approximately 0.508 m/s | Approximate conversion of vertical speed. |
18. PC symbols, keyboard shortcuts and practical characters
This overview is a practical cheat sheet for typing symbols on a computer, editing websites and writing technical or mathematical text. For special characters, the safest method is often to copy the character directly. Alt codes usually work in Windows when entered on the numeric keypad.
The ⧉ icon means copy. Click the icon next to a character to copy it to the clipboard. After copying, the icon briefly changes to ✓. The icon is shown only next to actual characters, not next to shortcuts such as Ctrl + C.
Where important characters are on CS / EN / DE keyboards
This table assumes common Windows keyboard layouts. English keyboards differ between US and UK layouts, especially for @, " and £. On laptops, some Alt codes may require a numeric keypad or copying the character directly.
| Character | Meaning | CS keyboard | EN keyboard | DE keyboard | Safe alternative |
|---|---|---|---|---|---|
( ) | parentheses | often Shift + 8, Shift + 9, or according to the key labels | US: Shift + 9, Shift + 0 | Shift + 8, Shift + 9 | copy the character |
[ ] | square brackets | often AltGr + F, AltGr + G | keys to the right of P | AltGr + 8, AltGr + 9 | Alt + 91, Alt + 93 |
{ } | curly braces | often AltGr + B, AltGr + N | Shift + [, Shift + ] | AltGr + 7, AltGr + 0 | Alt + 123, Alt + 125 |
< > | less than, greater than / angle brackets | < > key near the left Shift or Alt + 60, Alt + 62 | Shift + ,, Shift + . | < > key near the left Shift | <, > |
" ' | straight quote, apostrophe | according to the key labels; apostrophe is often on the accent key | US: Shift + ', '; UK often swaps @ and " | Shift + 2, apostrophe according to layout | ", copy the character |
“ ” | typographic quotation marks | usually not directly on the keyboard | usually not directly on the keyboard | usually not directly on the keyboard | copy the character or use Word |
/ | slash | according to the key labels or numeric keypad | key next to the right Shift | Shift + 7 | copy the character |
\ | backslash | often AltGr + Q | key above Enter or near the left Shift | often AltGr + ß | Alt + 92 |
| | vertical bar | often AltGr + W | Shift + \ | often AltGr + < | Alt + 124 |
@ | at sign | often AltGr + V | US: Shift + 2; UK: often Shift + ' | AltGr + Q | Alt + 64 |
# | hash | often AltGr + X | Shift + 3 | separate # key near Enter | Alt + 35 |
& | ampersand | often AltGr + C | Shift + 7 | Shift + 6 | & |
$ | dollar | according to key labels, often via AltGr | Shift + 4 | Shift + 4 | Alt + 36 |
€ | euro | often AltGr + E | not always direct on EN keyboards; often AltGr + 4 on UK | AltGr + E | Alt + 0128, € |
£ | pound sterling | usually not direct on CS keyboard | UK: Shift + 3; US usually not direct | usually not direct | copy the character |
~ ^ | tilde, caret | often via AltGr or dead keys | Shift + `, Shift + 6 | AltGr + +, ^ key | Alt + 126, copy |
° | degree sign | often Alt + 0176 | usually not direct on US keyboard | often Shift + ^ | ° |
² ³ | superscript 2 and 3 | often Alt + 0178, Alt + 0179 | usually not direct | often AltGr + 2, AltGr + 3 | ², ³ |
Characters better copied or entered via Alt / HTML
| Character | Group | CS / EN / DE keyboards | Recommended method |
|---|---|---|---|
≤ ≥ ≠ ≈ | mathematical comparison | usually not directly available on standard keyboards | copy the character or use Character Map |
± × ÷ √ ∞ | mathematics | usually not directly available on standard keyboards | ± can be typed as Alt + 0177; copy the others |
α β γ δ Δ λ π ρ σ Σ φ ω Ω | Greek letters | not directly on standard CS / EN / DE keyboards | copy the character, use Character Map, Word “Insert Symbol”, or HTML entities |
µ | micro | on DE often AltGr + M; on CS/EN copying is safer | µ or copy µ |
− – — | minus and dashes | usually not distinguished directly on the keyboard | for ordinary typing - is enough; for typography copy the correct character |
Basic Windows and browser shortcuts
| Shortcut | Meaning | Note |
|---|---|---|
Ctrl + C | Copy | Selected text, file or image. |
Ctrl + V | Paste | Pastes clipboard content. |
Ctrl + X | Cut | Moves selected content to the clipboard. |
Ctrl + Z | Undo | Reverses the last action. |
Ctrl + A | Select all | Text, files or page content. |
Ctrl + F | Find | Search within a page or document. |
Ctrl + S | Save | Document or file. |
Ctrl + P | Opens the print dialog. | |
Ctrl + T | New tab | In a web browser. |
Ctrl + W | Close tab | In a browser or document window. |
Ctrl + R | Reload page | Standard page reload. |
Ctrl + F5 | Hard reload | Reloads the page while bypassing part of the browser cache. |
Alt + Tab | Switch windows | Quickly switch between programs. |
Win + E | File Explorer | Opens the Windows file manager. |
Win + PrtScn | Screenshot | Saves a screenshot to the Pictures folder. |
Brackets and quotation marks
| Type | Characters | Use |
|---|---|---|
| Parentheses | () | Mathematics, text, functions. |
| Square brackets | [] | Text, links, programming. |
| Curly braces | {} | Programming, CSS, JavaScript, PHP. |
| Angle brackets / less than and greater than | <> | HTML tags, mathematics. |
| Straight quotation marks | "' | HTML, PHP, programming. |
| Typographic quotation marks | “”‘’ | Correct quotation marks in running text. |
Characters for web, HTML, PHP and programming
| Character | Name / meaning | Typical use |
|---|---|---|
< > | less than, greater than | HTML tags, mathematical comparison. |
/ \ | slash, backslash | Addresses, file paths, programming. |
| | vertical bar | Programming, separator, logical OR. |
& | ampersand | HTML entities, URL parameters. |
# | hash | HTML anchors, CSS colours. |
% | percent sign | Percentages, URL encoding, calculations. |
? = | question mark, equals sign | Parameters in links. |
+ - _ * | plus, minus, underscore, asterisk | File names, calculations, programming. |
~ ^ | tilde, caret | Technical notation, powers, programming. |
@ | at sign | Email addresses. |
; : . , | semicolon, colon, full stop, comma | Text, time, numbers, programming. |
Currencies
| Symbol | Currency | Note |
|---|---|---|
Kč | Czech koruna | Usually written after the amount: 100 Kč. |
€ | euro | Windows Alt code: Alt + 0128. |
$ | dollar | US dollar and other dollar currencies. |
£ | pound | British pound. |
¥ | yen / yuan | Japanese yen, Chinese yuan. |
Mathematical symbols
| Symbol | Meaning | Note |
|---|---|---|
+−×÷= | basic operations | Note: the mathematical minus − is not the same as the hyphen -. |
≠<>≤≥ | not equal, less than, greater than, less than or equal, greater than or equal | Comparing values. |
≈±%‰ | approximately, plus-minus, percent, per mille | Technical and approximate calculations. |
∞√∑∫ | infinity, square root, sum, integral | Mathematics and physics. |
Superscripts, subscripts and units
| Notation | Meaning / use | Note |
|---|---|---|
² ³ | second and third power | For example m², m³. |
⁻¹ | minus one | For example s⁻¹. |
m² m³ m/s² | area, volume, acceleration | Common technical units. |
km/h °C µm kWh | speed, temperature, micrometre, energy | Practical unit notation. |
Greek letters – main technical and mathematical symbols
| Letter | Name | Common use |
|---|---|---|
α | alpha | Angles, coefficients. |
β | beta | Angles, coefficients. |
γ | gamma | Coefficients, gamma radiation. |
δ Δ | delta, capital delta | Small change, difference, increment. |
ε | epsilon | Small quantity, error, strain. |
λ | lambda | Wavelength. |
μ µ | mu / micro | Coefficient of friction, micro prefix. |
π | pi | Circles and calculations with pi. |
ρ | rho | Density. |
σ Σ | sigma, capital sigma | Stress, standard deviation, summation. |
φ | phi | Angle, phase, diameter in technical text. |
ω Ω | omega, capital omega | Angular velocity, electrical resistance. |
Physical and technical symbols
| Symbol | Meaning | Example |
|---|---|---|
° | degree | 25 °C, 90°. |
′ ″ | minute, second | Angles or geographical coordinates. |
Ω | ohm | Electrical resistance. |
µ | micro | µm, µF. |
λ | lambda | Wavelength. |
π | pi | Circles and trigonometry. |
Δ | change / difference | Δt, Δp. |
≈ ± | approximately, plus-minus | Approximate values and tolerances. |
Special spaces and dashes
| Character | Name | Use |
|---|---|---|
- | hyphen | Compound words, file names. |
− | mathematical minus | Negative numbers and mathematical expressions. |
– | en dash | Ranges and inserted clauses. |
— | em dash | Long typographic dash. |
| non-breaking space in HTML | Between a number and a unit: 10 kg, 230 V, 25 °C. |
Useful HTML entities
| Character | HTML notation | Note |
|---|---|---|
< | < | Less than, beginning of an HTML tag. |
> | > | Greater than, end of an HTML tag. |
& | & | Ampersand. |
" | " | Straight quotation mark. |
€ | € | Euro. |
© | © | Copyright. |
® | ® | Registered trademark. |
° | ° | Degree. |
± | ± | Plus-minus. |
µ | µ | Micro. |
² | ² | Second power. |
³ | ³ | Third power. |
Note on CS / EN / DE keyboards: the exact position of characters differs depending on keyboard layout and Windows settings. Therefore this table mainly provides characters that can be copied directly, plus selected Alt codes or HTML notation.
Online unit converter conVERTER
For more extensive unit conversions, you may also use the Czech online unit converter conVERTER by Jiří Bureš.
This external link is published with the author’s permission. The converter opens in a new browser tab.