Observed Growing Degree Day Calculator
Accumulate heat units from consecutive daily temperatures with explicit base, upper threshold and capping method.
YOUR CALCULATION
Result
—
Calculation steps
Work through one step at a time or reveal the complete calculation. The steps use your current inputs.
How to calculate
Apply the selected capping convention to daily temperatures, subtract the base and accumulate daily heat units in the selected degree scale.
Mean cap: GDD=clamp((min+max)/2,base,upper)−base; separate caps: GDD=(clamp(min)+clamp(max))/2−base
Worked example
Min 5°C, max 20°C, base 10°C and upper 30°C give 5°C degree-days if each endpoint is capped first, but 2.5 if the raw daily mean is capped instead.
Assumptions and input details
These two named conventions can differ and are not interchangeable with every crop-specific GDD model. Thresholds and accumulated target are supplied by you; no universal stage, pest or treatment threshold is inferred. Data must have consecutive dates with min≤max. Celsius/Fahrenheit degree-day differences scale by 1.8 without a 32-degree offset. Up to 366 observed days; no weather retrieval or forecast.
References: Montana Climate Office: GDD methods and crop-specific thresholds
Using this calculator
Can I enter my own problem?
Yes. Replace the example values with your own inputs. The result, calculation steps, tables and applicable diagrams update from those inputs. Blank or invalid values clear the result; example values are never silently substituted for missing inputs.
Are the results exact?
Results use floating-point arithmetic and displayed rounding. Read the formula, assumptions and any stated data precision before interpreting the result.
Is my input uploaded?
The calculation runs in your browser. No account, file upload or external AI service is required. Inputs are not saved between page reloads.
Apply an entered constant growth or decay rate to an initial quantity. Compare periodic and continuous models, view a time curve and find doubling time or half-life.
Calculate sowing, hardening and scenario harvest dates from a user-supplied transplant reference date and crop durations.
Convert US or Imperial gpm, L/min, cubic meters per hour and cubic feet per minute.
Reserved advertising space.