Chill Hours Accumulation Calculator
Estimate total chill hours accumulated over a period from the average hours below 7°C per day.
Chill hours accumulate over the dormant season as the total hours below 7°C. Estimate the daily hours below 7°C from your night-time temperatures (more on cold, clear nights) and multiply by the days. Feed the total into a fruit's chill-requirement calculator to check if dormancy will break properly.
Indicative planning figures based on published research averages. Local soil tests, varieties and weather change actual requirements — confirm with your agronomist or extension officer.
Orchardists and growers use the free Chill Hours Accumulation Calculator for an accurate answer in seconds — no formulas to remember, works offline in the orchard.
About Chill Hours Accumulation Calculator
To know whether your orchard gets enough winter chilling, you need to accumulate chill hours across the dormant season. This tool gives the running total from the average hours per day spent below 7°C and the number of days — a quick way to project the season's chilling from typical night temperatures. Feed the result into the chill-requirement calculator for your specific fruit to judge whether dormancy and bloom will be normal.
How to use Chill Hours Accumulation Calculator
- 1Enter your values into the inputs.
- 2Read the headline result and the supporting breakdown.
- 3Apply the guidance in the note to your orchard decisions.
Why use Chill Hours Accumulation Calculator?
- ✓Uses the standard, citable formula
- ✓Clear inputs with sensible defaults
- ✓Instant result with the working shown
- ✓Free, fully in-browser and private
Frequently asked questions
How do I count chill hours?+
Add up every hour the temperature is below 7°C (45°F) through the dormant season. As a quick estimate, judge the average hours below 7°C on a typical day (more on cold, clear nights) and multiply by the number of such days, which this tool does.
Why 7°C for chill hours?+
Research found temperatures around 0–7°C are most effective at satisfying dormancy in temperate fruit, with the 7°C (45°F) threshold giving a simple, widely-used 'chill hours' model. More refined models (Utah units, chill portions) weight different temperatures, but hours below 7°C remains the common field standard.
Is this tool free and private?+
Yes — free, no sign-up, and all calculation runs in your browser, so it works offline in the orchard and your data never leaves the device.
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