The shop is not the square footage
Leases are written in square feet and merchandise is bought in linear feet, and the conversion between them is where most small fit-outs go wrong. Run the defaults: 2,400 square feet of shell becomes roughly 1,550 square feet of sales floor once a 22 percent stockroom and an eight-foot entry come off, and that sales floor yields about 300 feet of fixture face. Just under 68 percent of the sales floor is aisle, counter and circulation. That is not waste — it is the ordinary condition of a shop people walk around in — but it means the useful ratio is about 19 linear feet of face per hundred square feet of sales floor, and that ratio, not the lease, is what your buying is limited by.
The reason to know the face figure before signing anything is that it is the number your buying is limited by. A range that needs 40 feet of face is a seventh of this shop. Three of them and the perimeter, and you are full.
Runs come in whole numbers
Look at the aisle table and you will see it sit still and then jump. Across a 40-foot width with 18-inch wall fixtures and 48-inch runs, asking for 4.5, 5.0, 5.5 or 6.0 feet all give exactly the same answer: three runs, 6.25 feet of real aisle, 299 feet of face. The four specifications are the same shop. Ask for anything from 3.0 to 4.0 feet and you get four runs, 4.2 feet of real aisle and 365 feet of face — again all identical to each other.
So there are two shops available on this width, not a continuum, and the boundary between them sits between 4.0 and 4.5 feet. Everything you specify inside a band is decoration. That is why "we will just tighten the aisles a bit" is usually a wasted argument: either the width holds another run or it does not, and half a foot of drawing changes nothing at all until it crosses a boundary and then changes 66 feet of face at once.
Note what the calculator does with the slack. It does not leave the extra width at one end; it shares it across every aisle, because that is what a fixture crew does on the day. So the aisle you asked for is a minimum and the aisle you get is usually wider — at 4.5 asked for you get 6.25, nearly two feet more. Anyone specifying a run depth on the assumption that the aisles will end up tight has it backwards.
The productive version of the conversation is about run depth rather than aisle width, because the depth sits inside the same module. Dropping from a 48-inch double-sided run to a 36-inch one shortens the module by a foot, which across a 40-foot width is frequently the change that lets one more run in. It costs six inches of deck on every shelf in the shop, so it is a real trade — but it is a trade that actually moves the count.
The perimeter is the half people forget
At the defaults, the wall line contributes about a hundred feet of face, a third of the total, from floor that the runs were never going to use anyway. Wall fixtures are the cheapest face in the building: they stand on floor that has to exist for the walls to exist, they need no aisle of their own beyond the one already there, and they are visible from the door.
The share you can actually merchandise is the input that matters, and it is nearly always lower than people first say. Take out the entrance, the window returns, the fitting room doors, the stockroom door, the panel the electrical board is on, the fire alarm panel, the extinguisher, the till backing. Sixty-five percent is a starting guess for a shop with one door and a window run; measure the wall with a tape and mark the dead stretches before you trust it.
What this page will not decide for you
It will not tell you an aisle width. Clear widths for accessible routes, for egress, and for the number of people the floor is allowed to hold come from the code your jurisdiction adopted, from your building department and from an accessibility consultant, and they vary by occupancy and by state. Every dimension on the page is a number you supplied, and a layout that comes out of it is a sketch to take to those people, not an answer to give them.
The one thing worth saying plainly is about fixtures falling. Tall gondola runs, wall standards and freestanding displays are anchored to the structure for a reason, the top deck is where the heavy top-stock ends up, and children climb them. The fixing method is the manufacturer's, matched to what you are fixing it to. There is no procedure here on purpose.
Where the numbers go next
The face figure feeds the shelf facings and days of cover calculator, which turns a stretch of face into a facing count and tells you how often somebody has to refill it. The counter allowance connects to the checkout lane queue calculator, which sizes the queue space rather than guessing at it. The back-of-house percentage you entered here is tested for real by the stockroom size and delivery frequency calculator, which asks whether that strip actually holds a delivery. And once the shop is trading, the sales per square foot calculator divides the takings by this same floor split.
For the fixtures themselves, shelf spacing works out the clear height each deck gets, and shelf sag covers what a long unsupported deck does under load. Lighting layout and the flooring calculator handle the two trades that follow the fixture plan.
Questions people ask
How many linear feet of fixture does a small shop have?
It depends almost entirely on the aisle width and the run depth, which is why a per-square-foot rule is not worth carrying around. At the defaults here — a 60 by 40 shell, 22 percent back of house, 48-inch runs and a 4.5-foot minimum aisle — the answer is around 300 feet of face, or about 19 feet per hundred square feet of sales floor. Ask for a 4-foot aisle instead and the same shell gives 365 feet, a fifth more. Run your own dimensions, and treat the result as the ceiling on how many ranges you can carry rather than as a target to fill.
What aisle width should I use between gondola runs?
This page will not give you one, and you should be suspicious of any page that does. The clear width you need is set by the code your jurisdiction has adopted, by whether the aisle is part of an accessible route, by egress requirements for your occupancy, and by your building department, and those answers differ between two towns in the same state. The practical process is to get the required minimum from the people who enforce it, then decide how much above it you want for two people with baskets to pass, then bring that number here to see what it costs you in runs.
How much of the shop should be stockroom?
The honest answer is that it is set by how often you take deliveries, not by a percentage. A shop that receives twice a week needs to hold half of a week's cases plus a buffer; the same shop on a monthly delivery needs to hold four times that, and the difference is real floor. That is the calculation the stockroom and delivery frequency page does. What is worth saying here is that the trade is direct: every square foot of stockroom is a square foot the fixture plan does not get, and it is paid for at the same rent per foot.
Is deeper shelving better than more runs?
They pull against each other, because the run depth sits inside the same module as the aisle. A 36-inch double-sided run instead of a 48-inch one frees a foot per module, which across a typical width is often exactly enough for one more run — two more run lengths of face — at the cost of six inches of deck on every shelf in the shop. Whether that is a good trade depends on what you sell. Deep decks matter for boxed goods where units sit behind each other; they matter much less for hanging garments or for anything single-deep, where the extra depth just makes stock harder to see and to reach.
Do I need to bolt down retail fixtures?
Fixing requirements come from the fixture manufacturer and from what you are fixing to, and this page gives no method. What it does say is why the question is not optional: tall gondola runs, wall standards and freestanding display units go over when they are climbed, when they are hit by a cage or a pallet jack, and when the heaviest top-stock in the shop ends up on the highest deck. Children climb shelving. The people to ask are the fixture supplier and, where the structure is in question, an engineer, and the answer usually depends on the wall or the slab as much as on the fixture.