Calculate fertilizer rate and reapply date from actual temperatures
Rate, area & when to reapply
Features
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.
FAQ
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.