The short answer
They have the same 2 kg capacity and the same 0.1 g resolution. The Lunar is smaller, waterproof and responds in 10 ms, built for an espresso drip tray. The Pearl is larger with a 20 ms response, built for pour-over. Buy the one that matches how you brew - the accuracy is identical.
Side by side
Scroll the table sideways to see every column.
Quick picks
The answer first. Tap any row to jump to the full reasoning for that pick.
1. Choose this for espresso
Acaia Lunar
Upper-mid tier · A compact waterproof espresso scale sized for a machine drip tray.
Waterproof, 10 ms response, and sized for a drip tray.
The Lunar is designed for one environment: an espresso machine's drip tray. Its anodized aluminum body is fully waterproof - Acaia's position is that you can submerge it, dry it off and return it to use.
That matters because a drip tray is where scales die. Steam, backflush water and the occasional knocked cup are routine.
It publishes 2 kg capacity, 0.1 g resolution and a 10 ms response time. Ten milliseconds is fast enough to register the first drops of a shot accurately, which is what you need if you stop at a target yield.
The platform is deliberately small so it fits under a portafilter, and that makes it unsuitable for pour-over - a dripper and server will not sit on it stably.
Specification
- Capacity
- 2 kg
- Resolution
- 0.1 g
- Response
- 10 ms
- Body
- Anodized aluminum, fully waterproof
- Built for
- Espresso, on the drip tray
What it does well
- You can submerge it, dry it and carry on - that is not marketing
- 10 ms response keeps up with a shot starting
- Fits under a portafilter where a brewing scale will not
Where it gives ground
- The platform is too small for pour-over
- The most expensive way to weigh 36 grams of coffee
- Overkill unless you are chasing ratios shot to shot
Skip it if
Skip it if you brew pour-over. The platform is the wrong size and the Pearl exists for that.
2. Choose this for brewing
Acaia Pearl
Upper-mid tier · A brewing scale with a large platform, built for pour-over and batch brewing.
A large platform and a flow-rate display you can pour against.
The Pearl is the brewing scale: 2 kg capacity, 0.1 g resolution, and a 20 ms response time on a platform large enough to take a Chemex or a dripper sitting on a server.
That platform size is the practical difference, and it is why the two scales exist separately rather than one being a smaller version of the other.
The flow-rate display is where the Pearl earns its price for brewing. Pour-over technique is largely about how fast you add water, and a live grams-per-second reading turns that from a feel into a number you can repeat.
It is not waterproof, and it is too large for most espresso drip trays.
Specification
- Capacity
- 2 kg
- Resolution
- 0.1 g
- Response
- 20 ms
- Built for
- Manual brewing, home and shop
What it does well
- Big enough platform to sit a Chemex or a dripper and server on
- Fast and stable enough to pour against in real time
- Flow-rate display turns pouring into something you can measure
Where it gives ground
- Not waterproof - that is what the Lunar is for
- Too large to sit on most espresso drip trays
- Costs several times what a competent scale costs
Skip it if
Skip it if you only pull espresso. It will not fit under a portafilter and you would be paying for a platform you cannot use.
Why waterproofing is the real difference
The specification gap that matters in daily use is not the 10 ms of response time. It is that one of these scales survives being soaked and the other does not.
An espresso drip tray gets wet constantly: purging the group, backflushing, knocking a cup, the last drips after you pull the portafilter. A scale living there without water resistance is a scale on a timer.
Acaia's own position on the Lunar is that all the electronics and the LED screen carry a water-resistant coating and the aluminum body can be submerged and returned to use. That is an unusual claim and it is the reason the Lunar exists.
Does 10 ms versus 20 ms matter?
Less than the marketing implies, and not nothing. In espresso the first few grams arrive quickly, and a faster scale registers them with less lag - which matters if you are stopping the shot at a precise yield.
In pour-over, water arrives over two to three minutes. Twenty milliseconds is imperceptibly fast in that context, and the flow-rate display is doing far more useful work than the raw response figure.
If you want one scale for both
Neither of these is ideal at the other's job, which is an expensive problem to have. A mid-size scale like the Timemore Black Mirror Basic Plus - 152 x 130 x 26 mm, 2000 g at 0.1 g, with auto-timing and flow rate - is small enough for most drip trays and large enough for a dripper, at a fraction of either Acaia.
It is not waterproof and it is not as fast. For most home setups, those are acceptable trades for owning one scale instead of two.
Are either of them necessary?
No. A scale with 0.1 g resolution and a timer does the job, and a good one costs a small fraction of these. What Acaia sells is build quality, speed and - in the Lunar's case - genuine waterproofing.
If your grinder or your machine is the limiting factor in your coffee, spend the money there first. A better scale measures the same problem more precisely.