GDD Growth Stage Calculator

Q: "Do I need a weather API?"

"No. CSV or manual input is enough."

Q: "Can I use semicolon CSV from Excel?"

"Yes. Delimiters are auto-detected and decimal commas are accepted."

Q: "Should I use budbreak or full bloom?"

"Choose the reference your cultivar model uses. You can rename it freely."

Q: "How is the harvest forecast calculated?"

"The remaining GDD to the harvest threshold is divided by the recent daily GDD average."

Q: "Are the thresholds fixed?"

"No. The template values are only examples and should be edited for your cultivar and region."

Enter a budbreak or bloom date, add daily temperature data, and get the current growth stage and harvest forecast in one place.

No weather API is required. You can paste CSV, upload a file, or type rows by hand, then edit the stage profile to match your cultivar.

Works with CSV, file upload, or manual rows

Supports Celsius and Fahrenheit

Stage tables stay fully editable

Shareable state stays in the browser

Calculation assumptions

GDD thresholds vary by cultivar, region, tree age, vigor, crop load, and pruning. Edit the template values instead of using them as-is.
Harvest forecasts are estimates based on recent daily GDD averages. They can drift when temperatures swing sharply.
If your CSV has gaps, fill them before making decisions from the result.

CSV input format

The parser accepts comma, semicolon, or tab-delimited files and also tolerates decimal commas.

`date` is required. Accept `tmean`, or `tmin/tmax`, or `gdd`.
The parser auto-detects `comma`, `semicolon`, or `tab` delimiters.
Decimal values can be written as `12.5` or `12,5`.
A `gdd` column overrides temperature columns for that row.
`YYYY-MM-DD` is the recommended date format.

How to use

Enter the reference event and date. Choose budbreak, full bloom, or a custom label.
Set the temperature unit, GDD method, base temperature, and upper threshold if needed.
Paste CSV, upload a file, or add daily rows by hand.
Edit the stage profile, then review the current stage, next stage, and harvest forecast.
Copy the result or share the core settings with a URL.

Sample cases

From budbreak to the current stage

Input Reference date 2026-03-15, Celsius, base temperature 10°C, daily mean CSV, stage table: Budbreak 0 / Green tip 80 / Full bloom 160 / Petal fall 240 / Fruit set 320 / Harvest 500

Output Cumulative GDD 400.0 °C·day, current stage Fruit set, harvest forecast 2026-04-08

From full bloom to a harvest forecast

Input Reference date 2026-04-08, Fahrenheit, base temperature 50°F, upper threshold 86°F, semicolon CSV, forecast from the last 7 days

Output Cumulative GDD 286.0 °F·day, current stage Petal fall, harvest forecast 2026-07-02

Formulas

Daily GDD = max(0, min(input temperature, upper threshold) - base temperature)
Daily GDD = max(0, ((clipped Tmin + clipped Tmax) / 2) - base temperature)
Cumulative GDD = sum of daily GDD
Days to the next stage = next threshold - current cumulative GDD
Harvest forecast date = latest date + ceil(remaining GDD / recent average GDD)

Glossary

GDD

Growing degree days, or the accumulated effective heat used for growth models.

Base temperature

Heat below this threshold does not count toward GDD.

Upper threshold

A cap that prevents unusually hot days from contributing too much.

Reference event

The starting point for accumulation, such as budbreak or full bloom.

Growth stage

A milestone tied to a GDD threshold.

Forecast window

The number of recent days used to estimate future progress.

Frequently asked questions

Do I need a weather API?

No. CSV or manual input is enough.

Can I use semicolon CSV from Excel?

Yes. Delimiters are auto-detected and decimal commas are accepted.

Should I use budbreak or full bloom?

Choose the reference your cultivar model uses. You can rename it freely.

How is the harvest forecast calculated?

The remaining GDD to the harvest threshold is divided by the recent daily GDD average.

Are the thresholds fixed?

No. The template values are only examples and should be edited for your cultivar and region.

Stage template

Load the generic orchard template first, then edit it for your cultivar and region.
The stage names are editable. Keep the threshold values in ascending order.
Use `role=harvest` for the final row when you want the harvest forecast to stop there.