What is an FC/CYA chart?

An FC/CYA chart shows how much free chlorine you need at each cyanuric acid (stabilizer) level. Higher CYA protects chlorine from sunlight but also binds it, so the minimum effective FC rises with CYA. PoolTrack uses the TFP method: about 7.5% of CYA as the daily minimum, and 40% of CYA as the shock target.

What should free chlorine be if my CYA is 50?

At 50 ppm CYA, keep free chlorine at least 4 ppm, with a typical daily range of 4–8 ppm. Shock or SLAM that pool at 20 ppm FC. Enter your exact CYA in the lookup above to see the numbers for your water.

Do saltwater pools use a different FC/CYA chart?

The minimum FC is the same. Salt cells produce chlorine continuously, so the practical daily ceiling is a couple of ppm above the minimum instead of the wider chlorine-pool range. Most salt pools also run CYA higher (often 60–80 ppm) to protect the cell.

What if my CYA is above 80 or 100?

You can still sanitize the water, but you will need a lot more chlorine to stay effective, and shocking becomes expensive. The lasting fix is to lower CYA with a partial drain and refill, then hold FC at the new target. Do not add more stabilizer until CYA is back in range.

Is this the same chart PoolTrack uses in the app?

Yes. The public chart uses the same deterministic min, target, and shock functions as Today, the health check, and green-pool recovery. Create a free account if you want those targets saved against a real reading and retest.

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FC/CYA chart: what chlorine level you actually need

Cyanuric acid (CYA) is chlorine's sunscreen. More CYA means chlorine lasts longer in the sun — and you need a higher free-chlorine (FC) reading to keep the same killing power. Use the lookup, then read the chart.

Look up your CYA

Cyanuric acid (ppm)

Pool type

Min FC: 4 ppm
Daily range: 4–8 ppm
Shock / SLAM: 20 ppm

Chlorine-pool FC/CYA chart

Minimum FC is 7.5% of CYA (TFP method). Shock / SLAM is 40% of CYA, with a 10 ppm floor. These are the same numbers PoolTrack uses on Today.

Daily free-chlorine targets for a traditional chlorine pool.
CYA (ppm)	Min FC	Daily range	Shock / SLAM
No CYA	1 ppm	1–5 ppm	10 ppm
20	2 ppm	2–4 ppm	10 ppm
30	2 ppm	2–5 ppm	12 ppm
40	3 ppm	3–7 ppm	16 ppm
50	4 ppm	4–8 ppm	20 ppm
60	5 ppm	5–9 ppm	24 ppm
70	5 ppm	5–9 ppm	28 ppm
80	6 ppm	6–10 ppm	32 ppm
90	7 ppm	7–10 ppm	36 ppm
100	8 ppm	8–10 ppm	40 ppm

Salt-pool FC/CYA chart

The minimum does not change. Salt cells feed chlorine all day, so the practical daily ceiling stays a couple of ppm above the minimum. Most salt pools run CYA 60–80 to protect the cell.

Daily free-chlorine targets for a saltwater pool.
CYA (ppm)	Min FC	Daily range	Shock / SLAM
No CYA	1 ppm	1–3 ppm	10 ppm
20	2 ppm	2–4 ppm	10 ppm
30	2 ppm	2–4 ppm	12 ppm
40	3 ppm	3–5 ppm	16 ppm
50	4 ppm	4–6 ppm	20 ppm
60	5 ppm	5–7 ppm	24 ppm
70	5 ppm	5–7 ppm	28 ppm
80	6 ppm	6–8 ppm	32 ppm
90	7 ppm	7–9 ppm	36 ppm
100	8 ppm	8–10 ppm	40 ppm

Why the target moves with CYA

CYA binds a large share of free chlorine. The water can show 3 ppm FC on a strip and still be almost defenseless if stabilizer is high. That is why a pool at CYA 70 and FC 3 is sitting on an algae bloom even though the bottle says “ideal.”

Daily minimum: about 7.5% of CYA. Do not spend the afternoon below it.
Shock / SLAM: about 40% of CYA. Hold it there until FC barely drops overnight and the water is clear.
Indoor pools: little UV, so CYA can stay low (often 0–30) and FC targets stay small.

After you know the number

The chart tells you the target. It does not tell you how much liquid chlorine to pour, or whether yesterday's dose actually worked. That is the care-plan loop:

Dose from your current FC to the target. See the liquid chlorine dosing guide.
If the water is green, start the green pool recovery plan instead of guessing a shock bag.
Retest after circulation. Save the reading in PoolTrack so the next dose starts from what is actually in the water.