| Fertilizer | Unit | Current | On-order | Avg daily use | Lead time | Safety % | Reorder point | Recommended order |
|---|---|---|---|---|---|---|---|---|
| 20-20-20 Water-Soluble | kg | 8.0 | 2.0 | 0.15 | 10 days | 20% | 1.80 | 4.50 |
| Liquid Seaweed Concentrate | L | 3.5 | 0.0 | 0.06 | 7 days | 30% | 0.55 | 1.85 |
| Slow-Release Granules | kg | 12.0 | 0.0 | 0.08 | 14 days | 25% | 1.40 | 2.60 |
BaseDaily =
DailyUse
(direct mode)
or
BaseDaily =
(Area × RatePerArea) ÷ FrequencyDays
(application mode)
AvgDailyUse = BaseDaily × (1 + Wastage%/100)
LeadDemand = AvgDailyUse × LeadTimeDays
SafetyStock = LeadDemand × (Safety%/100)
ReorderPoint = LeadDemand + SafetyStock
ProjectedStock = CurrentStock + OnOrder
DaysOfSupply = ProjectedStock ÷ AvgDailyUse
RecommendedOrder = max(0, AvgDailyUse×TargetDays + SafetyStock − ProjectedStock)
- Enter current stock and any on-order quantity.
- Choose a usage method that fits your records.
- Add wastage, lead time, and safety stock settings.
- Set a target coverage window for your season.
- Press calculate, then export a report if needed.
Inventory visibility and mix accuracy
Consistent counts prevent overbuying and missed feedings. Record on-hand quantity after every mixing session, then add deliveries. Track concentrate, not diluted solution, and keep one unit per product. A small wastage factor covers spills, residue in scoops, and leftover mix that cannot be stored safely. Log package size, opening date, and remaining volume after each check for traceability.
Daily usage from programs or direct drawdown
When you know average drawdown, enter daily use and review it monthly. If you fertilize by schedule, compute daily use from area, dose rate, and application interval. This converts a weekly routine into per‑day demand and supports planning across beds, lawns, and container groups without guessing. Match area units to your rate, and avoid mixed measurements during setup.
Lead time, safety stock, and reorder point
Lead time demand equals average daily use multiplied by supplier lead days. Safety stock adds a buffer as a percentage of lead demand. The reorder point is the sum of both values. When projected stock drops below that line, ordering now reduces the risk of running out before delivery. Use the slowest delivery time seen in your last season logs.
Target coverage and purchasing discipline
Target days of coverage align inventory with the season. Short targets suit limited storage and fresh‑mix practices; longer targets suit remote gardens or bulk buying. Recommended order quantity fills the gap between projected stock and target inventory plus safety stock. Add unit price to estimate inventory value and purchase cost. Split large buys to reduce storage risk and waste.
Interpreting results and improving decisions
Days of supply is a clear signal: low days mean tighter monitoring, while high days can mean tied‑up cash or product aging. Recheck inputs after heat waves, rapid growth, or pest recovery, because demand shifts quickly. Keep notes on formulation changes and confirm the same settings before exporting reports. Rotate stock first-in, first-out to keep nutrients reliable always year-round.
1) What should I use for “daily use” if my schedule varies?
Average the last two to four weeks of usage, including busy weeks. If your program changes seasonally, run separate calculations for each phase and keep the most conservative value for reorder decisions.
2) How do I handle multiple fertilizers with different units?
Track each product in its own run using the unit that matches its packaging. Avoid converting mid-season unless you standardize measurements and update all related settings consistently.
3) What safety stock percentage is reasonable for home gardens?
Many gardens start with 15–30%. Increase it when deliveries are unreliable, growth is rapid, or you cannot shop quickly. Decrease it if you have stable suppliers and limited storage space.
4) Why does my recommended order show zero?
This happens when projected stock already covers your target days plus safety stock. You can lower target coverage to reduce holding, or keep the result and focus on using existing inventory efficiently.
5) Can I use the area method for container gardens?
Yes. Treat a container group as a single “area” unit, such as number of pots. Enter the dose per pot per application as the rate, and set the application interval in days.
6) How often should I update lead time and pricing?
Update lead time after each delivery if it changes, and review pricing when you switch suppliers or package sizes. Small updates improve reorder timing and cost estimates without changing your core feeding plan.