Notes on planning on the signal.
Demand planning, merchandising and inventory for modern retail brands — from the team building Tightly.
No, you can't ChatGPT your demand forecast
A chatbot predicts the next word, not a distribution over units. It hands you a confident number with no error bar and a different answer next run. That is the wrong tool for the forecast.
Why a forecast isn't a plan: bottom-up meets top-down
A single forecast, however good, is not a plan. Bottom-up and top-down have to be reconciled, or they drift apart by week three and you pay for the gap in inventory and markdown.
Open-to-buy is broken, and everyone in the room knows it
OTB became a quarterly spreadsheet nobody trusts by week three. Here is why it drifts, what the drift actually costs, and what open-to-buy looks like when it moves with sell-through.
The peak-season readiness checklist that actually holds up
Most brands over-prepare the pre-peak buy and neglect the in-season reaction. A real checklist covers all three phases: the plan you set, the triggers you watch, and the clear you run after.
Why your forecast and your plan never agree
The top-down financial plan and the bottom-up forecast start the season together and part ways by week three, because they live in different files. Here is how to reconcile them on one model.
The retail math that decides the season (and the decision each number should trigger)
Cover-weeks, sell-through, open-to-buy, GMROI: four numbers that run the season. Here is what each one means, and the specific decision it should trigger, because a metric that triggers nothing is decoration.
What tariffs actually do to your inventory plan
A tariff is a cost shock and a timing shock at once. It moves landed cost, open-to-buy and buy timing. You absorb it by re-plotting the buy, not by cutting across the board.
The markdown playbook: timing beats depth, every time
Most brands obsess over how deep to cut and get the timing wrong. The full markdown playbook: when to start, how far to go, and how often to reset. Timing does the heavy lifting.
Returns are demand too, and planning gross units is why you over-buy
DTC brands plan gross units and treat returns as an afterthought. That over-buys the high-return styles every time. Plan net, forecast the return rate by category, and the buy comes down where it should.
You are chasing newness and starving the range that pays the rent
Most brands over-invest in newness and under-invest in the continuity that funds the business. Here is why the split gets set backwards, and how to size it from demand.
The real reason brands over-buy (it is not the buyers)
Over-buying gets blamed on optimistic merchants. It is actually a forecasting failure, and once you can see it that way you can measure it, and fix it.
Why your size curves are quietly costing you a fortune
A blanket size curve sells out the middle and buries you in the ends. The cost hides in plain sight on the markdown report. Here is how per-door, per-style curves change the math.
"Last year plus a percentage" is not a forecast
Growing last year's number by a flat percent feels like planning. It is actually copying last year's mistakes forward and multiplying them. Here is what a trained model does instead.
Your sales history is not your demand history
Sales tell you what customers bought from what you had. Demand tells you what they wanted. Stockouts censor the gap, and it always makes your winners look smaller than they are.
A stockout costs you far more than the sale you lost
The lost sale is the smallest part of a stockout. You also lose the customer, force a substitution, and poison your own forecast. Availability at size and door is the real lever.
How to calculate open-to-buy (and why the number goes stale by week three)
The OTB formula takes five minutes to learn. The hard part is that a static open-to-buy is wrong the day you set it, because sell-through never reads the plan.
How to build a size curve that actually sells
A blanket national size curve sells out the middle and buries you in the ends. Build it per-style, per-door, from demand. Here is exactly how, with a worked example.
Lead time is the hidden variable in every buy
Lead time sets your cover-weeks, your reorder points, and how early a miss starts compounding. The longer the lead time, the more a slow signal costs you.
Demand planning and demand forecasting are not the same thing
Forecasting is the prediction. Planning is the decision you make with it. Conflating the two is why plans drift the moment reality disagrees with the forecast. Here is the line that matters.
Weeks of cover is not one number, and treating it like one costs you
A blanket weeks-of-cover target stocks out fast movers and drowns slow ones in dead stock. Set cover by category and lead time, from demand. Here is how, with a worked example.
How to read a sell-through report like a trader
A sell-through report is a set of positions, not a scorecard. Rate versus plan, by size and by door, tells you what to do this week. Here is how to read each cut and act on it.
The only markdown question that matters is when
Not how deep. When. The week sell-through tells you a style will not clear at full price is the week to act, and it almost never lines up with your promo calendar.
How to phase a season plan by month (without copying last year)
Most brands phase the season by pasting last year's monthly shape onto this year's total. The phasing errors that creates are silent margin leaks. Here is how to phase from demand instead.
Open-to-buy is a control loop, not a quarterly report
OTB is feedback control: a set point, a measurement, a correction. Run as a quarterly report, the loop is open, and an open loop cannot control anything.
Does a DTC brand need S&OP? Not the one you are picturing.
The heavyweight enterprise S&OP process, no. But a DTC brand absolutely needs a lightweight monthly reconcile of demand, buy and cash. Here is where the line sits, and why skipping it hurts.
How to lift sell-through without discounting a single unit
Discounting is the laziest way to move stock and the most expensive. The real levers are allocation, size curve, and reorder timing, and they lift sell-through with the buy you already placed.
Sell-through is the number to trade the season on
Sales flatters you and margin lags. Sell-through is the earliest honest signal of whether the season is working, which makes it the number you should actually run the business on in-season.
The first two weeks of a style tell you the whole season
A style's first 14 days are the most honest read you will get all season. Learn to read the two-week window and you can chase, hold, or exit while the whole season is still ahead of you.
The hidden cost of one extra week of cover
An extra week of cover feels like cheap insurance. It quietly ties up cash and pushes stock toward markdown. Here is the real math on over-covering.
Every markdown is a planning failure with a receipt
Markdowns feel like a sales problem. They are a lagging indicator of a buy or allocation decision made months earlier. Read them backwards and they tell you what to fix upstream.
Your ERP cannot plan, and it was never meant to
An ERP is a system of record. It documents the past accurately and has no opinion about the future. Bolting a plan onto it does not fix that. The plan belongs on top of the ERP, not inside it.
Plan with confidence. One set of numbers, every team, every week.
There's nothing to rip out. Tightly runs on your existing ERP, EDI, e-commerce and POS. Give us 30 minutes and we'll show it on your own categories.