Chill Requirement Agriculture Tools
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Chill hours and chill portions are different models, so this tool does not convert one into the other.
Chill hours use the basic 0.0°C to 7.2°C count, while chill portions use the Dynamic Model.
Daily max/min values alone are not enough. Use hourly or finer temperature records.
Tropical or evergreen fruit often do not need chill requirement calculations, so thresholds can stay empty.

Chill Hours / Chill Portions Calculator for Orchard Fruit

Calculate orchard chill accumulation from hourly temperature records and compare it with cultivar thresholds in the same workspace.

Built for temperate fruit orchards worldwide. Paste CSV, upload a file, or enter rows by hand, then export or share only the lightweight settings.

Works with hourly or finer temperature logs Supports chill hours, chill portions, and both together Keeps share links lightweight and browser-only Manual rows, CSV paste, upload, and JSON export

How to Use

  1. Choose the model mode and match the source temperature unit to your data.
  2. Paste CSV, upload a file, or enter hourly records in the manual table.
  3. Set the analysis range, orchard label, cultivar name, and optional thresholds.
  4. Review the chill cards, coverage, first reached time, and hourly preview.
  5. Copy the summary, export JSON for full restoration, or copy the lightweight share URL.

Examples

Temperate fruit with chill hours

Input
Hourly data from 2025-11-01 00:00 to 2025-11-17 15:00, temperatures around 5°C, threshold 380 CH
Output
400 CH, target met, +20 CH

Warm-climate orchard with chill portions

Input
The same hourly series, Dynamic Model enabled, threshold 12.5 CP
Output
13 CP, target met, +0.09 CP

Glossary

Chill hours

A basic chill count that adds hours between 0.0°C and 7.2°C.

Chill portions

A chill accumulation unit from the Dynamic Model that better handles warmer winters.

Endodormancy

A dormancy stage in which internal bud factors prevent growth.

Ecodormancy

A dormancy stage in which outside temperature controls growth resumption.

Formulas

  • CH = Σ(durationHours × countedFlag)
  • countedFlag = 1 when 0.0°C <= T <= 7.2°C
  • CP = DynamicModel(hourlyTemperatureSeries)
  • remaining = requirement - accumulated
  • progress = accumulated ÷ requirement

Frequently Asked Questions

Can I convert chill hours into chill portions?
No. They are different models, so compare each model only with the same unit.
I only have daily max and min temperatures.
That is not enough for this calculator. Convert the data to hourly or finer records first.
Is this useful for tropical fruit?
Usually not. Many tropical or evergreen fruits do not need a chill requirement calculation.
Why does this differ from another weather site?
Model definitions, cutoff rules, missing data handling, and the input time zone can all change the result.

Notes

  • Cultivar thresholds vary by region, publication, and bud type.
  • Keep all timestamps in the orchard's local time, and normalize daylight-saving changes before importing if needed.
  • If no threshold is entered, the tool still shows the accumulated value only.
  • Use this as a decision aid, not as the final basis for cultivar choice or frost protection.