Formula
- Use the units shown beside each field.
- Results update automatically whenever you change an input.
- Displayed values use up to four decimal places, or scientific notation for very small or large numbers. Calculations use standard floating-point arithmetic; exact integer and fraction tools identify their own precision rules.
- Original dimensions are positive integers. Target height is not rounded to a whole pixel; choose rounding separately if needed.
Example Calculation
- Original width: 1920
- Original height: 1080
- Target width: 1280 units
1920×1080 reduces to 16:9; width 1280 preserves the ratio at height 720.
Frequently asked questions
How do I use this calculator?
Enter original width, original height, target width. The result updates automatically. Use Reset to restore the example values.
What method does it use?
Reduce width:height by their greatest common divisor; target height=target width × original height/original width.. Original dimensions are positive integers. Target height is not rounded to a whole pixel; choose rounding separately if needed.
Why might a rounded result differ?
The calculation keeps full numeric precision internally, then rounds the displayed result. Rounding intermediate steps by hand can produce a slightly different answer.
Are my inputs saved online?
No. This calculator processes your inputs in your browser. A recently used list stores only calculator names on this device, not your entered values.
Check the assumptions and units before using this result. Read about calculation methods.