PoolDoseLog - Pool Chemical Calculator & Water Test Log
PoolDoseLog is a water test log and chemical calculator for people who look after their own pool or hot tub. You describe the water once — how many gallons or litres it holds, whether it runs on chlorine, bromine or a salt generator, and which products you buy — and from then on every test you enter turns into a short list of what to add and roughly how much.
Each suggestion can be opened to show how it was worked out: the water volume, the gap to your target, the product strength and the coefficient used. pH is not handled with a single multiplier; the calculator uses your alkalinity and stabiliser (CYA) readings, because both change how much acid or soda ash a pool really needs.
Everything you enter stays in this browser. There is no account, and the log, dose history and charts keep growing for as long as you use it.
The app runs entirely in your browser. What you enter is saved only on this device.
How to use PoolDoseLog
- Add your pool. Give it a name, choose pool or hot tub, chlorine, bromine or salt water, and whether it is outdoors. Enter the volume, or let the app estimate it from the shape (rectangle, round, oval or freeform), length, width and average depth.
- Pick targets and products. Choose a target preset (Standard, TFP style or Manufacturer) and the products you actually use: liquid chlorine 12.5% or 10%, cal-hypo, dichlor or trichlor; muriatic or dry acid; soda ash or borax; and calcium chloride. Targets stay editable later.
- Log a test. Tap Log a test and type what your kit or strip reads. Leave anything you did not measure blank. You can attach a photo of the strip and a note.
- See what to add. Save and see doses opens a list of suggested amounts. Open a card to read the calculation, and add products one at a time, letting the water circulate between them.
- Record what you added. Tap I added this and adjust the amount to what you really poured. The dose is saved with the test, next to the suggested amount.
- Watch the trend. The History tab lists every test, charts each reading against its target band and shows the dose log. In Settings you can switch to metric units and download a backup or CSV file.
Features
- Dose estimates for chlorine, bromine, pH up and down, alkalinity, calcium hardness, stabiliser and salt
- pH calculation that accounts for alkalinity and cyanuric acid
- Side effects shown, such as stabiliser added by dichlor or alkalinity lowered by acid
- Dilution advice when calcium, CYA or salt is too high
- Optional chlorine target that follows your CYA level
- Editable target ranges and three presets
- Test history, charts and a dose log with optional cost tracking
- US or metric units
- CSV export of tests and doses, CSV import of tests, ZIP backup and restore
How pool chemical doses are worked out
Start with an accurate volume
Almost every dose is "so much product per part per million (ppm) per 10,000 gallons", scaled to your pool. If the volume is 20% too high, every dose is 20% too high. For a rectangle, multiply length × width × average depth in feet by 7.48 to get gallons; round pools use the diameter instead. If you are unsure, err on the low side and top up after retesting rather than overshooting.
Why product strength matters
Raising free chlorine by 1 ppm in 10,000 US gallons takes about 38 grams of available chlorine. That is roughly 10 fl oz of 12.5% liquid chlorine but closer to 13 fl oz at 10%, and products lose strength as they age in the heat. Stabilised tablets and granules also add cyanuric acid, and cal-hypo adds calcium, which builds up over a season.
pH and alkalinity work together
Total alkalinity is the water's buffer. The higher it is, the more acid it takes to move pH down, and the faster pH tends to drift up. Stabiliser also buffers, so the same pH change needs a different amount of acid in a pool with CYA 30 than in one with CYA 80. Adjust alkalinity first, then pH, and make pH changes in small steps.
Chlorine and stabiliser
Cyanuric acid protects chlorine from sunlight but also slows it down. A common rule of thumb keeps free chlorine at about 7.5% of the CYA level or more, so a pool at CYA 40 wants roughly 3 ppm or higher. Indoor pools and hot tubs usually need little or no stabiliser.
Some things only come out with fresh water
No chemical removes cyanuric acid, salt or calcium hardness. When they climb above range, the practical fix is to drain part of the water and refill. To halve a reading you replace about half the water.
Handle chemicals safely
Read the label first and follow it. Add one product at a time with the pump running, and give it time to mix before the next. Never mix chemicals with each other — chlorine and acid together release toxic gas — and always add chemicals to water, not water to chemicals. Wear gloves and eye protection, work with good ventilation, and store products dry, apart and away from children. If the water does something you do not understand, ask a pool professional.
Frequently asked questions
Where is my data stored?
Only in this browser on this device, in its local storage and IndexedDB. There is no account and nothing is uploaded. Clearing your browser's site data deletes the log, so download a ZIP backup from Settings > Backup now and then.
How accurate are the doses?
They are estimates based on your readings, the volume you entered and typical product strengths. Test kits, old product and a wrong volume all add error. Add part of the dose, circulate, and retest before adding more. The product label always takes priority.
Can I see how a number was calculated?
Yes. Open any dose card for the breakdown, or turn on Show the calculation in Settings to have the cards open by default.
Does it work for hot tubs and bromine?
Yes. Choose hot tub as the type and bromine as the sanitiser; the targets and visible readings adjust, and stabiliser is not suggested for bromine.
Do reminders send notifications?
Not on the web. You can still set test and maintenance reminders; when one is due it appears on the Pool tab, where you can mark it done.
What does the phone app add?
The iPhone and Android app sends reminder notifications, keeps automatic weekly backups on the device, and offers Premium features: more than one pool, a season summary with a PDF report, and the calcium saturation index.
Limitations of the web version
- One pool or hot tub on the web; multiple pools, the season summary, PDF reports and the saturation index are in the phone app's Premium
- Reminders appear on the Pool tab when due, but no notifications are sent
- No automatic weekly snapshots; download a ZIP backup from Settings > Backup instead
- Backups, CSV files and strip photos stay in this browser unless you download them
Disclaimer
PoolDoseLog's calculations are estimates, not instructions. Always read and follow the product label. Never mix chemicals with each other, never mix chlorine with acid, and add chemicals to water rather than water to chemicals. Work in a well-ventilated place, wear gloves and eye protection, and keep chemicals away from children and pets. Add part of a dose and retest before adding more, and consult a pool professional when in doubt.
Phone app
PoolDoseLog is also available as an app for phones and tablets: