You drop a compressor on a vocal, leave the ratio at the default 4:1, and tweak the threshold until the meter shows a few dB of gain reduction.
The vocal sounds fine, but you have no idea why 4:1. Was that the right number? Should it have been 2:1? 8:1?
You move on, secretly hoping the choice did not matter.
The setting that controls how hard the compressor squeezes is the ratio, and the difference between 2:1 and 8:1 is the difference between transparent control and a brick wall.
Pick the wrong number and the same source will sound either invisible or crushed flat, regardless of what you do with the threshold.
This post walks you through what each ratio actually does, which numbers fit which sources, and the decision framework that lets you pick a ratio in five seconds instead of guessing for twenty minutes.
TL;DR
- 1.5:1 to 3:1: transparent. Use for buses, mastering, gentle leveling.
- 3:1 to 6:1: the workhorse range. Vocals, drums, bass, guitar.
- 6:1 to 10:1: aggressive. Snare, kick, parallel compression.
- 10:1 and up: behaves as a limiter. Peak control only.
- The rule: match the ratio to the source’s natural dynamics, not the genre.
The goal of this post is to help you understand which ratio to start with for any source, why the same number behaves differently on a vocal versus a drum bus, and the three mistakes that turn a useful ratio into a flat mix.
What Compressor Ratio Actually Is
Ratio is the math that decides how much the compressor turns the signal down once it crosses the threshold.
A 4:1 ratio means that for every 4 dB the input goes over the threshold, the output only rises by 1 dB.
The other 3 dB get squashed. A 2:1 ratio cuts the overshoot in half. A 10:1 ratio reduces it to almost nothing.
An easy mental model: think of the ratio as the fraction of the signal that survives compression above threshold.
2:1 lets half through. 4:1 lets a quarter through. 8:1 lets an eighth through. At infinity:1, nothing past the threshold is allowed out, which is the definition of a limiter.
That is the whole concept.
The interesting part is what happens to the perceived character of the source as you move the ratio knob, because identical gain-reduction readings can sound radically different depending on whether you got there with a 2:1 ratio and an aggressive threshold, or a 10:1 ratio and a gentle one.
How Each Ratio Sounds in Practice
Numbers on a knob do not tell you what your ear hears. Two compressors set to the same gain reduction can sound completely different if their ratios are different.
The shape of the reduction matters more than the amount.
- 1.5:1 to 2:1: the listener cannot tell the compressor is on. Useful for bus glue and gentle leveling.
- 3:1 to 4:1: audible only when bypassed. The signal feels tighter and more present.
- 6:1 to 8:1: you can hear the compressor working. The source feels controlled, sometimes pumped, often punchy.
- 10:1 and up: the compressor becomes the texture. Snare smashes, parallel crush, peak limiting.
The shift from “transparent” to “audible” usually lives between 4:1 and 6:1.
That is also where most beginner mistakes happen: a 6:1 ratio with 6 dB of gain reduction sounds great on a snare and terrible on a lead vocal.
Same numbers, different source, opposite outcomes.
Want to see your own track’s dynamic range without opening a plugin? Drop your file into the Compression Analyzer.
Settings Reference: 1.5:1 to Infinity:1
Use this table as a starting reference.
The “feel” column is what listeners describe when each range is used correctly. The “use case” column is the most common application.
None of these are rigid rules.
They are the patterns that show up across mixes that work.
| Ratio | Intensity | Feel | Typical Use |
|---|---|---|---|
| 1.5:1–2:1 | Very gentle | Invisible glue | Mix bus, mastering, leveling |
| 2:1–3:1 | Gentle | Smooth, polished | Acoustic guitar, BVs, ballad vocal |
| 3:1–4:1 | Moderate | Tight, present | Lead vocal, bass, drum bus |
| 4:1–6:1 | Firm | Controlled, punchy | Pop vocal, kick, electric guitar |
| 6:1–10:1 | Aggressive | Audible, pumped | Snare, parallel comp, room mics |
| 10:1–20:1 | Heavy | Smashed, glued | Drum smash, aggressive parallel |
| 20:1+ / ∞:1 | Limiting | Brick wall | Peak control, mastering ceiling |
Starting Points by Instrument
The right ratio depends on the source’s natural dynamics and the role the part plays in the mix.
A vocal that has to sit on top of a busy chorus needs more control than a fingerpicked acoustic in a sparse arrangement.
The numbers below are the values you reach for first.
Lead vocals
Start at 3:1 for ballads and pop verses, push to 4:1 or 5:1 for choruses or rap. Vocals are dynamic, but the listener is sensitive to how a voice “breathes.”
Anything past 6:1 on a single compressor will start sounding squashed.
If you need more control, use two compressors in series at 3:1 each. Vocal-specific attack and release settings matter as much as the ratio choice here.
Drums (individual)
Snare loves 4:1 to 8:1 with a fast attack to clamp the transient.
Kick is gentler at 3:1 to 4:1 because the body matters as much as the click. Toms work at 4:1 with medium attack to let the resonance through.
Each piece of the kit responds differently because the transient-to-body ratio differs.
Drum bus
2:1 to 3:1 with slow attack, fast release, 2 to 4 dB of gain reduction.
The job here is glue, not control. The individual drums already have their own compression. The bus pulls the kit together as one element.
Bass guitar
4:1 with a medium attack (10–30 ms). Bass is the foundation of the mix and needs to sit at a consistent level.
A 4:1 ratio handles the dynamic peaks without flattening the body that gives bass its weight.
For DI and amped tracks blended together, compress them separately at 3:1 each and let the bus do the rest.
Mix bus and mastering
1.5:1 to 2:1, with 1 to 3 dB of gain reduction across the whole song. The job is to make the parts feel like a single piece of music, not to control dynamics.
Anything past 2:1 on a finished mix usually flattens the production. For more on master-bus dynamics, see the complete audio compression guide.
Ratio vs Threshold: Which to Move First
Ratio and threshold work together to decide how much compression you get and how it feels. Most beginners reach for the threshold first and leave the ratio at whatever the preset chose.
That is backwards.
The ratio decides the character of the compression. The threshold only decides how often the compressor engages.
- Pick the ratio first based on the source. Use the table above.
- Pull the threshold down until you see 3 to 6 dB of gain reduction on the loudest passages.
- If 6 dB feels like too much, do not back the threshold off. Lower the ratio instead.
- If 6 dB feels too gentle, do not push the threshold harder. Raise the ratio instead.
This procedure is the difference between a compressor that is “doing its job” and one that is fighting the source.
For the underlying mechanics of every control involved, the complete walkthrough of using a compressor covers each parameter in order.
Try it on anything: a vocal, a drum bus, a full mix. Launch the Compression Analyzer → It takes about 5 seconds per file.
Three Mistakes That Flatten Mixes
The same three patterns show up over and over in mixes that feel dull or lifeless. None of them are about the wrong plugin.
They are about misreading what the ratio is for.
- Leaving every preset at 4:1. A 4:1 ratio is right for a lead vocal. It is wrong for a drum bus, wrong for a master, and wrong for a fingerpicked acoustic. Pick the ratio for the source, not the preset.
- Using high ratios as a peak-control trick. If you need to catch occasional spikes, that is a job for a limiter or a clipper, not a compressor at 10:1. Compressors at high ratios with low gain reduction sound nervous and inconsistent, because they are only triggering on the loudest moments.
- Stacking 4:1 ratios in series without a plan. Three compressors at 4:1 each, all hitting 3 dB of reduction, sounds completely different from one compressor at 4:1 hitting 9 dB. The serial chain is more transparent, but only if each stage has a clear job. Otherwise it just stacks distortion.
Ready to stop guessing? The Compression Analyzer will show your track’s best settings that fit your actual source, not a generic preset.
Frequently Asked Questions
The questions below come up most often when intermediate producers start getting serious about compression.
Each answer leads with the rule, then explains why.
What is the difference between 2:1 and 4:1 compression?
A 2:1 ratio reduces overshoot above the threshold by half. A 4:1 ratio reduces it to a quarter. Practically, 2:1 is transparent and used for bus glue or mastering.
4:1 is the workhorse for vocals, drums, and bass, where you want noticeable but musical control.
The same gain reduction with 2:1 vs 4:1 will feel softer and more natural at 2:1, tighter and more present at 4:1.
What does an 8:1 compression ratio do?
An 8:1 ratio reduces a 4 dB overshoot to 0.5 dB above the threshold.
It is firmly in audible compression territory and works well on snares, parallel buses, and any source where you want the compressor to be part of the texture.
On lead vocals or master buses, 8:1 will sound squashed unless the gain reduction is kept under 2 dB.
What is the best compressor ratio for mastering?
1.5:1 to 2:1 with 1 to 3 dB of gain reduction. The job of a mastering compressor is to glue the mix together, not to flatten dynamics.
Anything past 2:1 on a finished master usually compresses the production rather than enhancing it.
For peak control on the master, use a limiter at infinity:1, not a compressor at high ratio.
Is a higher compressor ratio always better?
No. Higher ratios sound more processed, not more polished.
A 10:1 ratio on a vocal flattens the dynamic gestures the singer made, even if the meter shows the same gain reduction as a 3:1 setting.
Use the lowest ratio that gets the source to sit in the mix.
If you need more, raise the ratio in small steps and listen for the moment the source starts feeling controlled rather than transparent.
What ratio should you use on vocals?
3:1 is the most common starting point for lead vocals. Push to 4:1 for choruses, rap, or pop production. Pull back to 2:1 for ballads and intimate verses.
Background vocals usually want 2:1 to 3:1 since they sit lower in the mix and need less individual character. Two compressors at 3:1 in series often sounds better than one at 6:1.
When does a compressor become a limiter?
Once the ratio reaches 10:1 or higher, the compressor behaves more like a limiter. At 20:1 and above it is a limiter for practical purposes.
True limiters use ratios of infinity:1 with a very fast attack to ensure no peak ever crosses the ceiling. Use a dedicated limiter for peak control.
A compressor at high ratio is not the same tool, even when the math looks similar.
The Bottom Line
Pick the ratio for the source, not the preset.
2:1 for transparent work, 3:1 to 4:1 for vocals and drums, 6:1 and above when you want the compressor to be heard.
Move the threshold to control how much, not how. Master that distinction and most of the “what should I use” questions answer themselves.
And if you would rather skip the meter-reading altogether, the Compression Analyzer gives you the ratio recommendation along with the attack and release in about 5 seconds.
If you want to go further on specific applications, these are worth your time:
- Parallel Compression Explained
- Mix Bus Compression Settings
- Crest Factor: How Much Compression Your Track Needs