Search "best lead time calculator tools" and you get a ranked list with the publisher at #1, plus a generic SCM suite that wants to own the network. Wrong job if you import finished goods. The question is not which logo wins a trophy. It is whether you need a calculator that splits production, transit, and customs, a sheet you will actually update, or an inventory module that treats lead time as one field.
I wrote this as the approach page for importers. When a calculator is enough, when Sheets still holds, and when Cin7, Inventory Planner, or Katana is the right shape. Not a supply-chain software roundup.
If you need the trigger math, use the reorder point formula for importers. Model the legs in the free lead time calculator. Stay here when you are choosing how to keep the number honest.
If The Factory Said 30 Days And Sellable Was 65
You import finished goods for Amazon FBA, Shopify, or both. Demand is knowable enough to use a daily rate. Lead time is production plus ocean plus the day the unit is sellable, not ex-factory.
Skip an enterprise planning suite if you do not have a network-design problem or an S&OP cycle. Those tools solve a real problem. A founder with four factories will spend the year configuring a plan they do not run.
Skip a formal tool altogether if you have three SKUs and you already reorder from a calendar you trust. Write the last inbound in days and buy a few days earlier than that. Do not dress a guess up as a calculator.
Lead Time Is Production Plus Transit Plus Customs
The factory's "30 days" is usually production. It is not the clock you plan with.
For an importer, lead time is the days from PO sent to sellable received:
- Production, including the slip after Chinese New Year or a missed cutoff
- Transit, including a rolled sailing
- Customs, brokerage, and exams
- Final delivery and receiving into FBA or the warehouse
The free lead time calculator adds production, transit, and customs. The safety buffer sits on top. It is not part of lead time. How to calculate safety stock is the buffer page. This page is how you keep the three legs from collapsing into one stale cell.
Do not stop the clock at factory completion or vessel departure. A unit on the water is not a unit you can sell.
Worked: They Reordered On 32. The Clock Was 65.
SKU sells 24 units a day.
The factory quoted 32 days. That number went into the sheet as "lead time." Ocean was "about three weeks" in a freight email. Nobody put it in the trigger. Customs was assumed to be a day or two.
Last inbound, measured to the day the unit was sellable:
| Leg | Days |
|---|---|
| Production (quoted 32) | 34 |
| Ocean transit | 23 |
| Customs and exam | 8 |
| PO sent to sellable | 65 |
Safety stock on this SKU is 240 units (10 days of cover). Chosen reserve, not a Z-score. The safety stock page is how you build a better one.
They used the quote:
(24 × 32) + 240 = 1,008 unitsThe actual clock:
(24 × 65) + 240 = 1,800 unitsThat 792-unit gap is 33 days of sales. It is where the stockout starts, and where the air-freight invoice comes from. The quote was a sales input. The 65 was the operating input.
The reorder point page uses a different SKU (18 a day, 52-day actuals, 600 safety, trigger 1,536). Same mistake, different numbers. Do not copy 52 onto this SKU. Measure this inbound.
Run the same legs through the lead time calculator: 34 production, 23 transit, 8 customs, 24 daily demand, 10-day buffer. If the result is nowhere near the number you used to send the last PO, you do not have a planning system. You have a cell.
A Calculator, When You Need The Legs Tonight
A web calculator is the right first tool when you are about to send a PO and you do not trust the factory's one number.
The SupplyAutomate lead time calculator is built for that hour. Enter production, transit, and customs. Add a safety buffer in days. Add daily demand and current stock if you have them. You get lead time, a planning horizon (lead time plus the buffer), a reorder point, and the latest date the next PO can go out.
It is free. No signup. It will not read an invoice. It will not remember last month's inbound. It will not guess the lane from a freight booking. That is the point. You still have to type honest days.
Use it to kill a bad plan on a call: factory 28, ocean 22, customs 6 is already 56 before anyone talks about FBA receiving. Use it again when a shipment slips, with the new dates, not the original quote.
A calculator fails when you treat the output as a policy and never refresh it. The form is only as current as the last inbound you measured.
A Spreadsheet, When You Own The Dates And The Catalog Is Small
A sheet is still the most honest first system. One row per SKU. Factory, lane (air vs ocean), last three PO-to-sellable dates, average, the quote you are ignoring, daily demand, safety days, reorder point.
It holds while SKU count is small, one person owns the file, and someone updates the dates when a container rolls. Templates exist for this on purpose.
The usual collapse is not a formula error. Production slip lives in WeChat. The rolled sailing lives in a freight email. The sheet still says 32. Reorder point drifts. You find out the week FBA goes red.
A sheet also dies when three people edit it, when you run air and ocean on the same SKU without splitting the rows, or when the trigger has to sit next to a landed-cost target and an open PO. At that point you are maintaining a rumor.
Keep estimated and actual in separate columns. If you overwrite the quote with the actual, you lose the variance. If you never record the actual, the quote survives forever.
Inventory And MRP Modules, When Lead Time Is Already A Field You Run
Some brands do not need a standalone calculator. They already run a system that stores lead time as an input to reorder or production. The question is whether that field is the importer clock, or a single number nobody updates.
Cin7 And Peers, If Locations And Channels Hurt More Than Dates
Inventory platforms such as Cin7 Core put lead time into reorder rules across warehouses and channels. If overselling and location counts are the actual pain, buying a purchasing module on that stack is more honest than forcing a calculator to be a WMS.
Ask to see a factory date change that is not a stock receipt, and a lead time that splits production from ocean from customs. A lot of this category is strong after the goods land and thinner before they do. Lead time is often one field.
If stock, not supplier dates, is the constraint, read the ecommerce inventory management guide. Do not buy Cin7 to replace a 20-minute calculator.
Inventory Planner, If Demand Swings Are The Bottleneck
Forecasting tools treat lead time as an input to a demand model. Useful when seasonality and sell-through are the reason you buy late. Weak when the reason is a factory that slipped 12 days and a customs hold that added 8.
Inventory Planner will not break the inbound into legs. It will not read a commercial invoice. It will not replace a reorder point you cannot defend. Pair it with measured actuals, or you will forecast accurately on a 32-day lie.
Katana And Peers, If You Kit Or Build
MRP calculates lead time across a bill of materials. That matters when a finished SKU waits on the slowest component. Finished-goods importers do not get much from component depth they will never use.
Test whether a finished-goods PO with ocean freight and a duty hold is a first-class object or an awkward workaround. If you do not have a BOM, this is the wrong shape.
How To Pick The Approach
Pick for the decision in front of you.
| Situation | Use | Do Not Use |
|---|---|---|
| You are about to send a PO and the factory quote is the only number | The lead time calculator | A platform trial |
| A handful of SKUs, one owner, dates you will update | A sheet | A second inventory app |
| Locations and channels already disagree | Inventory software (Cin7 and peers) | A calculator as a WMS |
| Seasonality is the miss, dates are already honest | A forecasting tool | A forecasting tool fed a stale lead time |
| You assemble from components | MRP (Katana and peers) | MRP for straight import/resell |
| Dates, documents, and unit cost have to live on the PO | An importer workspace | Another static lead-time cell |
Whichever you use, rebuild one active SKU from the last three inbounds. Production, transit, customs, receiving. Compare that average to the number in the sheet. That audit finds the 32-versus-65 gap faster than another ranked list.
Where SupplyAutomate Sits, And Where It Does Not
SupplyAutomate is not a one-shot form. It is not Cin7. It is built for Amazon FBA and Shopify importers who want the purchase order, the supplier documents, and the dates on one record so lead time is not a chat.
Upload the invoice and the packing list. Match them to the PO. See promised versus actual. Use that number in the next reorder point. Start with the lead time calculator when you need a planning number tonight. Use the product when delayed invoices and a growing catalog make the sheet a rumor.
It will not invent a lead time you never recorded. It will not replace a WMS. Multi-warehouse pick-pack and shop-floor MRP are different jobs. One SKU and a stable lane can stay on a spreadsheet.
FAQ
What Is A Lead Time Calculator?
A tool that turns the inbound into a number you can plan with: days from PO sent to sellable stock. The useful versions split production, transit, and customs instead of storing one factory quote. Some also return a reorder point and the latest safe order date.
Does Lead Time Include Customs And Receiving?
It should. A calculator that only tracks order-to-ship misses exams, holds, drayage, and FBA or warehouse receiving. Those legs are often the ones that turn a 32-day quote into a 65-day inbound.
Is A Spreadsheet Lead Time Calculator Good Enough?
Yes, while SKU count is small and one person updates the dates when a shipment slips. It fails when the quote stays in the cell and the actual lives in email. Past that, you need a record, not a prettier formula.
How Do You Calculate Reorder Point From Lead Time?
Average daily sales on days you had stock, times actual lead time in days, plus safety stock. The reorder point formula is the trigger page. This page is how you stop feeding it the factory's 32.
Is Cin7 Better Than A Lead Time Calculator?
Cin7 is better once locations and channels are the constraint, because lead time feeds reorder rules across warehouses. For a single-channel importer who needs the legs tonight, a calculator or a sheet is the smaller tool. Do not buy a platform to replace three numbers.
Can Inventory Planner Calculate Lead Time By Itself?
It uses lead time as an input to demand forecasting. It does not break production, transit, and customs into stages. If suppliers missing dates is the problem, measure the inbound first. Then let the forecast use that number.
A calculator is only useful if someone updates it when the inbound changes. Rebuild one SKU from the last three PO-to-sellable dates, then compare that average to the number you used to send the last order. The lead time calculator is that rebuild. The reorder point page is what you do with the result. If the quote and the documents already disagree, the next tool you need is a record, not a ranked list.