Video Compression Ratio Calculator
Dashcam videos can take up a surprising amount of space, especially when you save long trips or keep footage from multiple cameras. The Video Compression Ratio Calculator shows how the size of an original video compares with the size of a compressed copy. Enter both file sizes in megabytes (MB), and the calculator expresses the result as a ratio relative to 1.
The ratio helps you understand how much smaller a file has become. It does not tell you whether the compressed footage is clear enough to read a license plate, see a road sign, or review an incident.
What the Video Compression Ratio Calculator does
The calculator divides the original file size by the compressed file size. For example, if an original dashcam video is 1,000 MB and its compressed copy is 200 MB, the result is 5.00:1. This means the original file is five times the size of the compressed file.
A larger ratio means the compressed copy is smaller relative to the original. A 5:1 ratio represents a greater file size reduction than a 2:1 ratio. If the result is 1:1, the files are the same size. A result below 1:1 means the compressed file is actually larger than the original.
Use this video compression ratio calculator when comparing a dashcam recording with a copy you have exported, converted, or compressed. It can also help you compare the storage impact of different copies of the same recording.
How to use the Video Compression Ratio Calculator
- Find the original file size. Check the file properties or information for the video before compression. Enter that size in the Original file size (MB) field.
- Find the compressed file size. Check the properties of the compressed or exported copy. Enter that size in the Compressed file size (MB) field.
- Read the Compression Ratio. The result appears as a number followed by :1, rounded to two decimal places.
Both entries must use the same unit. The fields are labeled in MB, so convert sizes shown in other units to MB before entering them. Use a consistent conversion for both files, particularly if one device displays a size in gigabytes and another displays it in megabytes. The calculator accepts values from 0.01 MB to 10,000,000 MB in each field.
For the most useful comparison, choose an original file and a compressed copy containing the same footage. If you trim the video as well as compress it, the ratio reflects both the shorter duration and any changes made during compression.
How the Video Compression Ratio Calculator formula works
The formula is straightforward:
Compression Ratio = Original file size ÷ Compressed file size
The result is written as the original size relative to 1. With the calculator’s default values, the worked example is:
- Original file size: 1,000 MB
- Compressed file size: 200 MB
- Calculation: 1,000 ÷ 200 = 5
- Compression Ratio: 5.00:1
In this example, the compressed file is one-fifth of the original size. It is also 80% smaller than the original. These are two ways to describe the same size comparison: the compression ratio is 5:1, while the percentage reduction is 80%.
To calculate percentage reduction separately, subtract the compressed size from the original size, divide that difference by the original size, and multiply by 100. For the example above, that is (1,000 − 200) ÷ 1,000 × 100 = 80%. The calculator displays the ratio, so the percentage is a separate calculation.
As another example, a 750 MB original and a 300 MB compressed copy produce 750 ÷ 300 = 2.50:1. The compressed copy is 60% smaller than the original. Comparing examples like these can help you interpret the result without confusing a ratio with a percentage.
Use cases for the Video Compression Ratio Calculator
Managing dashcam storage: If you save footage to a computer or external drive, comparing original recordings with compressed copies can show how much their file sizes differ. This can help you plan how much footage you may be able to keep, although actual sizes vary between recordings.
Preparing a clip to share: A smaller file may be easier to upload or send when a service has a file size limit. Calculate the ratio after creating a copy, then check the actual compressed file size against the limit. The ratio alone does not confirm that the file meets a particular service’s requirements.
Comparing export settings: You can create copies of the same clip using different settings and calculate a ratio for each one. This gives you a clear size comparison. Watch each copy as well, because the smallest file may not preserve the details you need.
Organizing an archive: If you are considering compressing a collection of recordings, a sample comparison can give you an initial sense of the potential space savings. Treat that sample as an assumption, not a guarantee: footage with different lengths, motion, lighting, and recording settings can produce different results.
Reviewing an incident: A compressed copy can be convenient for sharing footage with another person. Before relying on it, check whether important details remain visible and whether the full relevant sequence is included. Consider keeping the original recording available when it may be needed.
Other factors to consider when calculating Compression Ratio
File size is not the same as video quality. The calculator measures the relationship between two file sizes only. It cannot assess sharpness, motion, color, audio, or whether a license plate is readable. A high compression ratio may save space, but you need to inspect the resulting video to decide whether it meets your needs.
Compare equivalent footage. If the compressed file has been trimmed, cropped, or had audio removed, its smaller size may not be due to compression settings alone. Differences in duration and content affect the ratio, so note any edits when comparing files.
Recording and export settings matter. Resolution, frame rate, bitrate, codec, and audio settings can all affect file size and playback. Two compressed files with the same size ratio may look different, depending on the original footage and how each file was encoded.
Dashcam footage can be difficult to compress consistently. Rain, moving traffic, nighttime lighting, and rapidly changing scenes can affect the relationship between file size and visible detail. Check representative sections of your own video, especially the moments that matter to you.
Rounding can hide small differences. The calculator displays two decimal places, so ratios that are close together may appear identical after rounding. For precise storage planning, also compare the file sizes themselves.
Compression can increase file size. Converting an already compressed video using different settings may produce a larger file. In that case, the calculator returns a ratio below 1:1. For example, a 200 MB original and a 400 MB output produce 0.50:1.
Video compression ratio FAQ
What does a 5:1 video compression ratio mean?
It means the original video is five times the size of the compressed copy. For example, a 1,000 MB original and a 200 MB compressed file produce a 5:1 ratio. In that example, the compressed file is 80% smaller.
Is a higher compression ratio always better?
No. A higher ratio indicates a smaller output file relative to the original, but it does not tell you how the video looks or sounds. Choose a file size that suits your storage or sharing needs, and review the footage for details you need to retain.
Can I enter file sizes in GB instead of MB?
The calculator fields are labeled in MB, so convert GB values to MB before entering them. The ratio works with any matching unit, but both values must use the same unit and a consistent conversion.
Why is my compression ratio below 1:1?
A ratio below 1:1 means the compressed or exported file is larger than the original. This can happen when the output uses settings that produce a larger file. Check both file sizes and confirm that they are entered in the correct fields.
Does the ratio show whether dashcam footage is clear enough?
No. It shows the change in file size, not the visibility of road signs, license plates, or other details. Play the compressed copy and inspect the relevant sections before deciding whether it is suitable for your purpose.