34 gardening calculators
Each one solves a specific gardening problem with ZIP-keyed data, methodology on-page, and provenance to NOAA or USDA.
Last Frost Date Lookup
Average last spring frost for your ZIP, in 50/30/10% probability bands.
First Fall Frost Date
When to expect your first cool night — and your harvest deadline.
Seed Starting Date
When to start vegetable seeds indoors based on last frost + crop.
GDD Tracker
Daily growing degree days — track your crop's heat-unit accumulation.
Chill Hours Accumulator
Winter chill hours for stone fruit, blueberries, perennials.
Frost Risk Probability
Re-derive frost dates at 30% / 10% risk levels.
Season Length
Days between last spring frost and first fall frost.
Companion Planting
Are these two crops good neighbors?
Container Size
Gallons of soil needed per plant by crop.
Drip Irrigation
Emitter spacing & flow planning.
Mulch Coverage
Cubic yards of mulch needed at any bed size.
Fertilizer NPK
Calc exact nutrient ratios.
Soil Amendment
Lime, gypsum, sulfur dosing plans.
Raised Bed Soil
Soil volume needed at any length × width × depth.
Harvest Date Estimator
Expected harvest window from transplant date + days-to-maturity.
Transplant Date
When to move seedlings outdoors for optimum survival.
Succession Planting
Multiple sowing dates for continuous harvest.
Daylight Hours
Hours of sun your garden gets by date + latitude.
Square Foot Garden
Cells per bed by crop density.
Vertical Garden
Crops per tower by trellis height.
Pollinator Garden
Plant list for bee-friendly borders.
Cover Crop
Mix and seeding-rate planning.
Crop Rotation Planner
4-year rotation by family.
Compost Quantity
Yard waste to usable compost, by feedstock.
Rain Barrel
Storage volume for roof catchment.
Evapotranspiration
Daily water demand by crop.
Watering Schedule
Frequency and depth by soil type.
Seeds to Buy
Total seeds (germ loss + oversow factor).
Yield Estimator
Per-plant yield for vegetables.
Days-to-Plant
Countdown to sow/transplant/harvest.
Row Spacing Planner
Rows + plants fit your garden.
Fence / Trellis Height
Wind protection + trellis geometry.
Rain vs Supplemental
When to skip watering based on recent rain.
Soil pH by Crop
Check whether your soil pH falls inside the optimal band for 27 crops.
22 crop planting guides
Companions, antagonists, soil temps, spacing, days-to-maturity, pest alerts, harvest notes — sourced to public-domain extension publications.
All 26 USDA hardiness zones
Full USDA Plant Hardiness Zone Map 2023, with localized frost dates, GDD, daylight, chill hours, and crop recommendations per zone.
| Zone | Winter Low | Growing Season | Avg Last Frost | Avg First Frost |
|---|---|---|---|---|
| 10a | 30°F – 35°F | 340 days | Mid to late January | Late December / frost-free in most years |
| 10b | 35°F – 40°F | 360 days | Early January | Frost-free in most years; occasional late December frosts |
| 11a | 40°F – 45°F | 365 days | Frost-free year-round | Frost-free year-round |
| 11b | 45°F – 50°F | 365 days | No frost ever | No frost ever |
| 12a | 50°F – 55°F | 365 days | No frost ever | No frost ever |
| 12b | 55°F – 60°F | 365 days | No frost ever | No frost ever |
| 13a | 60°F – 65°F | 365 days | No frost ever | No frost ever |
| 13b | 65°F – 70°F | 365 days | No frost ever | No frost ever |
| 1a | -60°F – -55°F | 92 days | Late May | Late August / early September |
| 1b | -55°F – -50°F | 105 days | Mid-late May | Early September |
| 2a | -55°F – -50°F | 110 days | Mid to late May | Early September |
| 2b | -50°F – -45°F | 120 days | Early to mid May | Early September |
State-specific planting calendars
Planting calendars and frost dates for 20 states. Each page includes month-by-month planting guide and zone-by-zone breakdown.
Guides
Understanding USDA Hardiness Zones
Read the guide →
How Frost Dates Work
Read the guide →
Growing Degree Days Explained
Read the guide →
Companion Planting Basics
Read the guide →
Crop Rotation Guide
Read the guide →
Seed Starting Indoors Step-by-Step
Read the guide →
Succession Planting Explained
Read the guide →
About SproutZones
Free, no signup, no tracking. Data sources: USDA Plant Hardiness Zone Map 2023, NOAA NCEI 1991–2020 climate normals, and public extension service publications.
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