Formula used
The model calculates each crop separately. Effective crop area is multiplied by plant density, system density, crop yield per plant, crop cycles, germination, survival, marketable percentage, remaining crop percentage, growing-system performance, environmental performance, and pollination where applicable.
Marketable annual yield = area × density × system density factor × yield per plant per cycle × cycles per year × germination × survival × marketable rate × remaining crop rate × system yield factor × environmental factor.
Daily irrigation demand = plant count × crop water rate × system water factor × climate water factor ÷ irrigation efficiency × demand remaining after rainfall contribution.
Design roof load = saturated media + beds and equipment + stored water + plant biomass + protected structure + people and tools + weather allowance. The total is divided by gross area and multiplied by the safety factor.
Annual net profit = crop revenue − annual operating costs. Payback equals initial cost divided by positive annual net profit. All outputs should be calibrated with local crop records and professional site information.
How to use this calculator
Start with measured roof dimensions. Reserve realistic percentages for drains, utilities, parapets, access, emergency paths, equipment zones, and surfaces that cannot be planted. Vertical levels should represent actual racks or towers, not an aspirational multiplier.
Describe the rooftop microclimate. Enter sunlight, shade, wind, climate, water reliability, pollination, and protected-environment improvements. Use manual adjustments only when local trial data supports them.
Build a crop plan. Add one row for every crop and system. Leave override fields at zero for library defaults, then replace those defaults with supplier specifications, extension guidance, or farm records.
Check water and media. Enter irrigation efficiency, rainfall contribution, water-storage days, media depth, and saturated density. Stored water and wet media are major rooftop loads.
Complete structural inputs. Add equipment, greenhouse, people, tools, rain, and snow allowances. The average-load result cannot determine safety; concentrated tanks, beam spacing, columns, membrane condition, wind uplift, and anchoring still require professional review.
Enter every meaningful cost. Include assessment, waterproofing, irrigation, tanks, tools, installation, nutrients, electricity, labor, maintenance, packaging, transport, permits, insurance, and replacements.
Review ranges, not one number. Compare conservative, expected, optimistic, and simulation results. Lower percentiles are useful for contingency planning when weather, price, or operational performance is uncertain.
Save and export. Store projects in the browser, export JSON backups, download CSV data, create share links, and print the page to PDF. Shared links may be long for multi-crop projects.
Planning assumptions and limitations
Built-in values are editable planning benchmarks. Cultivar, season, skill, pest pressure, and market standards can materially change results.
Crop allocation uses effective area. Media load converts it to a physical footprint using entered vertical levels.
Default cycles equal 365 divided by climate- and system-adjusted cycle length. Add cleanup delays through overrides.
Water demand is an annualized crop model. Peak hot-day demand may exceed the displayed daily average.
Average load cannot establish safety. Point loads, dynamics, uplift, deterioration, and local codes remain outside this model.
Revenue assumes marketable output sells at the average entered price. Taxes, finance, depreciation, and working capital need separate treatment.
Crop minutes per plant are combined with general weekly labor. Mechanization, travel, packing, and skill affect actual hours.
The simulation is illustrative and does not reproduce weather sequences, correlated failures, disease outbreaks, or market shocks.
Household coverage compares kilograms only. It does not test nutrition, preference, seasonality, or storage losses.
Rooftop farming planning guide
Begin with safety, access, and drainage
A rooftop farm should begin with drawings, membrane inspection, drainage mapping, parapet review, fire access, electrical capacity, material-handling routes, and professional structural assessment. Water is especially important because one litre has approximately one kilogram of mass. Tanks, deep-water systems, wet growing media, and clustered containers can create concentrated loads that an average-area calculation cannot reveal. Overflow routes should protect the building during pump, valve, or storm failures.
Match crops to the real microclimate
Leafy greens and herbs often fit compact hydroponic production and rapid succession planting. Fruiting crops need stronger light, trellising, pollination, water, and longer cycles. Root crops need sufficient media depth. Dwarf fruit plants need large containers and long investment horizons. High wind can tear foliage, increase evaporation, reduce pollination, damage structures, and create uplift forces.
Calibrate the model with pilot cycles
Record germination, survival, planting density, first-harvest date, marketable mass, water use, nutrient use, labor minutes, rejects, prices, and customer demand. Replace generic values with rolling averages after several cycles. Conservative assumptions are safer when financing or building commitments depend on projected production.
Plan the whole harvest workflow
Growing area alone does not create sellable produce. Reserve space for propagation, nutrient mixing, sanitation, tool storage, sorting, packing, temporary cooling, compost handling, and waste removal. Stagger plantings to avoid harvest peaks that exceed labor, storage, or customer demand.
Use results as a decision range
The expected result is not guaranteed. A resilient project should still cover essential water, safety, and operating needs under a lower-yield outcome. Update the calculation whenever roof plans, supplier quotes, crop records, energy prices, or sales channels change.