What TDS Actually Means in Coffee (and Why It Changes How Your Cup Tastes)
When coffee professionals talk about a coffee being "strong" or "weak," they often mean two different things. The strength — how much of the coffee is actually dissolved in the cup — is one thing. The extraction — how much of the available coffee material was pulled out of the grounds — is another.
TDS, or total dissolved solids, is the measurement that separates them.
This is what TDS means, how it's measured, and why the number matters when you're brewing coffee at home.
The simple definition
TDS stands for total dissolved solids. In brewed coffee, it's the percentage of the cup's mass that came from dissolved coffee compounds, with the rest being water.
A typical brewed coffee has a TDS of somewhere around 1.15% to 1.45%. That means a cup that's 250 grams of brewed coffee contains about 2.9 to 3.6 grams of dissolved coffee material, with the rest — about 246 to 247 grams — being water.
When someone says a coffee is "strong," they usually mean it has a high TDS — more dissolved coffee per cup. When someone says a coffee is "weak," they usually mean it has a low TDS — less dissolved coffee per cup.
This is different from extraction. Extraction is the percentage of the coffee grounds that actually dissolved into the cup. If you brew 18 grams of coffee and end up with 3.3 grams of dissolved material in the cup, you've extracted 18.3% of the grounds by mass.
A coffee can be high TDS (strong, lots of dissolved material) but low extraction (you didn't pull much out of the grounds). Or low TDS (weak) but high extraction (you pulled out a lot of what was available). These give very different cups.
How TDS is measured
In cafés and coffee labs, TDS is measured with a refractometer — a small instrument that measures how light bends when it passes through a liquid. Coffee with more dissolved solids bends light more than water. The refractometer reads that bend and translates it to a TDS percentage.
Home brewing has gotten easier to measure in the last decade. There are now inexpensive digital TDS meters (often sold as coffee refractometers or honey refractometers) that you can use to check your brew. They're not lab-grade, but they're close enough to be useful.
The alternative is to estimate TDS from your recipe. If you know your coffee dose (18 grams), your water dose (300 grams), and your brew ratio (1:16.7), you can estimate the TDS based on typical extraction yields for your brewing method. This is less accurate than a refractometer but works for most home brewers.
What TDS numbers mean for the cup
Different brewing methods target different TDS ranges:
- Pour-over (V60, Chemex): typically 1.20% to 1.45%
- French press: roughly 1.20% to 1.35%
- Espresso: 8% to 12% (much higher — espresso is a much stronger brew)
- Cold brew concentrate: 5% to 8%
- Drip coffee maker: 1.15% to 1.35%
These ranges overlap, but they give you a sense of how each method relates to the others. Espresso is fundamentally a different strength beverage than drip or pour-over — it's closer to a cold brew concentrate than it is to a typical American cup.
A pour-over or drip coffee in the 1.15% range will taste thin and weak to most people. One in the 1.45% range will taste strong and full. Most home brewers aim for somewhere around 1.25% to 1.35% — a balance of strength and clarity.
TDS vs extraction — the two-axis framework
This is where the science gets interesting. Strength and extraction are independent variables, and a coffee can be high or low on either axis independently. The Specialty Coffee Association (SCA) describes the "brewing control chart" — a 2x2 grid where:
- X-axis: TDS (strength, 1.0% to 1.5%)
- Y-axis: Extraction yield (16% to 22%)
- Optimal zone: roughly 1.15% to 1.35% TDS and 18% to 22% extraction
A coffee in the optimal zone is balanced — strong enough to feel substantial, extracted enough to have developed its flavors. A coffee outside the optimal zone will have a noticeable flaw:
- Low TDS, low extraction: thin, sour, undeveloped
- High TDS, low extraction: heavy, harsh, often bitter
- Low TDS, high extraction: weak but clean, sometimes described as "tea-like"
- High TDS, high extraction: heavy and full but can be harsh if extracted too far
The two-axis framework helps you diagnose bad cups. A cup that's both strong and harsh is likely over-extracted — you need to grind coarser or brew shorter. A cup that's thin and sour is likely under-extracted — you need to grind finer or brew longer. A cup that's thin but not sour is just weak — you need more coffee or less water.
Why this matters for home brewing
Most home brewers don't measure TDS. They go by taste. That's fine — taste is the ultimate measure of whether a cup is good. But TDS gives you a way to talk about strength objectively, and it lets you compare different brew methods on the same scale.
If you brew the same coffee as both pour-over and French press, you can measure the TDS of each. The pour-over will likely come in at the higher end of the range, the French press at the lower end. The pour-over will taste brighter and more focused; the French press will taste heavier and more rounded. Both can be good.
If you want to experiment with strength, try brewing the same coffee at two different ratios. A 1:15 ratio will give you a higher TDS than a 1:17 ratio. The 1:15 cup will taste stronger. Some coffees taste better strong; others taste better more dilute. It's worth finding the ratio that suits each coffee.
A simple home experiment
If you want to play with TDS at home, here's an easy experiment:
- Brew the same coffee two ways: 18 grams coffee to 360 grams water (1:20 ratio) and 18 grams coffee to 270 grams water (1:15 ratio). Use the same grind, same water temp, same pour technique.
- Taste them side by side. The 1:20 cup will taste lighter and more delicate. The 1:15 cup will taste stronger and more present.
- If you have a refractometer, measure the TDS of each. The 1:20 cup will likely come in around 1.10% to 1.20%. The 1:15 cup will likely come in around 1.30% to 1.45%.
- Decide which you like better. That's your preferred strength for that coffee.
Different coffees taste better at different strengths. A delicate washed African coffee often tastes better on the lighter end. A heavier-bodied Brazilian or Sumatran coffee often tastes better on the stronger end.
The takeaway
TDS is a tool for thinking about coffee strength objectively. It's not a rule for how to brew — your preference matters more than any measurement. The reason to know about TDS is that it gives you a vocabulary for talking about strength, and it helps you diagnose cups that aren't working.
If your morning coffee tastes thin and sour, the answer is probably more coffee or finer grounds. If it tastes heavy and harsh, the answer is probably less coffee or coarser grounds. TDS is the measurement that lets you see which one you're doing.
Brew slow. Sip slow.
— The Cozy Sips team
P.S. We've written about what extraction percentage means and what body means in a coffee cup if you want to dig deeper into the science.