The bag says 70 days — but that assumes 25°C. FertClock uses real temperatures to show how much fertilizer is left and when to feed again. Every formula shown.
Rate, area & when to reapply
Fertilizer does not run out on a calendar. It runs out on temperature.
The bag says "70 day type" — but that number assumes 25°C. In a cool spring the same product lasts 117 days. In midsummer it is gone in 58. FertClock uses the actual temperatures at your plot to tell you how much is still working and when to feed again.
WORK OUT THE RATE
- Enter your area, or measure it: tap the corners on the satellite map, or walk the bed with AR
- Pick a blend — 10-10-10, 8-8-8, 46-0-0 and more — or type your own N-P-K
- Get the total to spread AND the amount per square metre, side by side
- Bags to buy, with the leftover shown
WATCH IT RUN DOWN
- A graph shows the nitrogen still in the soil, day by day
- Solid line where real temperatures were measured, dashed where forecast
- Base dressing and top dressing stack up on the same chart
- The next feeding date, with the days remaining
EVERY NUMBER SHOWS ITS WORK
- Tap any result to see the formula, the values put into it, and the answer
- Degree-days are listed one day at a time, so the running total adds up
- Constants are printed in full — ln(5) = 1.609438 — so you can check it on a pocket calculator
- No hidden model. This is not a paid feature; it is how the app works
GARDEN, LAWN, FIELD
- Kitchen garden: g/m², planter counts, per-planter amounts
- Lawn: annual nitrogen budget, warm- and cool-season, lb/1000 sq ft
- Field: kg/10a, ares and hectares, base and top dressing
QUIET BY DESIGN
- No account, no ads, no subscription — one price, yours forever
- Works offline. Only the weather comes from the network
- Location is optional: type temperatures in by hand if you prefer
FertClock estimates from what you enter and from weather data. The figures are a guide — the product label, your soil, and local guidance come first. It does not select products, diagnose soil, or predict yield, and it does not guarantee results.
Work out the rate
Enter your area, or measure it with a satellite map or AR. Pick a blend like 10-10-10 or enter your own N-P-K. Get total to spread and per square metre side by side.
Watch it run down
A graph shows the nitrogen still in the soil day by day. Solid line for real temperatures, dashed for forecast. Base and top dressing stack on the same chart.
Every number shows its work
Tap any result to see the formula, the values put into it, and the answer. Degree-days listed one day at a time. Constants printed in full so you can check on a calculator.
Three modes
Kitchen garden: g/m² and planter counts. Lawn: annual nitrogen budget, warm or cool season. Field: kg/10a and bag counts.
Quiet by design
No account, no ads, no subscription. Works offline except for weather. Location is optional.
Why use temperature instead of days?
The 70-day type on a fertilizer bag assumes 25°C. In a cool spring the same product lasts 117 days. In midsummer it is gone in 58. FertClock uses your actual temperatures to show how much fertilizer is left.
Does FertClock collect personal data?
No. All calculations happen on your device. Location is optional and used only to fetch weather, not stored.
Does it work without internet?
Yes, except for weather forecast. You can type temperatures in by hand if you prefer.
What does FertClock not do?
It does not select products, diagnose soil, or predict yield. The figures are a guide — your product label and local guidance come first.
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