Tare, fill, weigh, pay

Zerena Store — A package-free, zero-waste bulk shop | zerenastore.com

What this format is

A weighing routine: tare an empty container, fill from bins holding 10–25 kg of stock, and pay net grams multiplied by a unit price per kilo that EU rules require on the label.

What it is not

Not an automatic discount and not a subscription scheme — savings depend on comparing unit prices, and nothing is delivered, booked or sold on this page; it explains the format rather than operating it.

400–700 gtare of an empty 1-litre glass jar, deducted at the scale

10–25 kgtypical capacity of one gravity bin on the shop floor

6–8 monthspantry life of flour at 15–25 °C — the shortest staple on the shelf

How does a zero waste store work, step by step?

Weigh the empty container, fill it, weigh again — you pay the net weight times the unit price per kilo.

The format replaces packaging with a weighing routine. You bring a jar, bag or bottle, and the scale records its empty weight before any product touches it. That figure — the tare — is subtracted from everything that follows.

Dispensing is by gravity bin or scoop. Gravity bins hold 10–25 kg of stock and release it downward into your container; scoops run from 60 ml (a quarter cup) to 240 ml (a full cup) for smaller goods. Either way, the filled container goes back on the scale.

Payment is net weight multiplied by the shelf's unit price per kilo. Because the tare was recorded first, the packaging never appears on the receipt — the only grams you pay for are the ones you eat.

Step 1 — Tare the empty container: the scale subtracts its weight (400–700 g for a 1-litre glass jar, 30–60 g for a cotton bag). Typical failure: the forgotten tare, where the jar's grams get charged as food.
Step 2 — Fill from a gravity bin holding 10–25 kg of stock, or with a scoop sized 60–240 ml. Typical failure: the headspace overfill — product heaped above the rim that spills at the scale.
Step 3 — Reweigh and check the maths: net grams multiplied by the unit price per kilo. Typical failure: the unzeroed scale — always look for 0.00 before the jar goes on.
Step 4 — Label with product and date, then rotate at home: flour within 6–8 months, dried beans within 2–3 years, sealed white rice beyond 2 years. Typical failure: the mixed batch — new rice poured over old, so the older grains never get used.

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What does your container add to the scale?

Between 30 and 700 grams, depending on material — choose the tare so the packaging never outweighs the goods.

A 1-litre glass jar weighs 400–700 g empty, depending on wall thickness. That range is wide enough to matter: at the heavy end, the jar approaches the weight of a full litre of long-grain rice (0.85 kg) before the lid even goes on.

Fabric is the light alternative. A cotton produce bag adds only 30–60 g of tare, and a 1-litre HDPE bottle kept for refills weighs 30–50 g — one reason liquid refills still travel home in plastic at a packaging-free shop.

The skill is matching tare to goods. Dense products forgive a heavy jar: honey runs about 1.4 kg per litre, so even a 700 g jar is outweighed by its contents two to one. Light goods punish heavy glass, which is why experienced shoppers keep bags for the light stuff and jars for the heavy. The gram-by-gram table sits on the container tare weights page.

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The numbers on the shelf edge

The numbers a bulk shop runs on: container tare, product density and dispenser volumes.
Item	Typical figure	Unit	What it tells you
Empty 1-litre glass jar	400–700	g	Tare deducted at the scale before filling
Empty cotton produce bag	30–60	g	Lightest tare — best for light, low-priced goods
Empty 1-litre HDPE bottle	30–50	g	Single-use packaging avoided with each refill
Honey	1.40	kg per litre	Denser than water — a litre overreads the kilo
Olive oil	0.92	kg per litre	Lighter than water — a litre underreads the kilo
Long-grain rice	0.85	kg per litre	A litre jar holds only 0.85 kg
Gravity bin capacity	10–25	kg	Stock volume behind each dispenser on the floor
Bulk scoop	60–240	ml	Quarter-cup to full-cup portions by volume

The numbers a bulk shop runs on: container tare, product density and dispenser volumes.

Terms used at the scale

Tare: The weight of an empty container. The scale's tare button subtracts it before filling, so you pay for net product weight only.
Net weight: The weight of the goods alone: filled weight minus tare. This is the figure multiplied by the unit price at checkout.
Unit price: The price per kilogram or litre shown on the shelf label, required on food above 100 g or 100 ml — and above 50 g or 50 ml for herbs and spices — under EU price-indication rules.
Gravity bin: A bulk dispenser that holds 10–25 kg of product and releases it downward into your container.
Bulk scoop: A measuring scoop for loose goods, typically 60 ml (a quarter cup) to 240 ml (a full cup). It measures volume, not weight.
First in, first out: The pantry rotation rule: older stock is used before newer stock, so nothing outlives its shelf-life months at the back of the shelf.

How is the price per kilo displayed?

EU price-indication rules require a unit price per kilogram or litre on food above 100 g or 100 ml — and above 50 g or 50 ml for herbs and spices.

The unit price sits on the shelf label next to the selling price. Because the thresholds are written into EU price-indication rules, even the smallest jars on the spice wall — from 50 g or 50 ml up — carry a comparable per-kilo figure.

This is the comparison tool for the whole shop. It puts a 250 g supermarket pack, a loose scoopful and a 10 kg gravity bin on the same unit, so the question of whether bulk is cheaper has an arithmetic answer rather than a feeling.

To check any fill: net grams divided by 1000, multiplied by the unit price, equals what you pay. The thresholds, the division and the density traps are set out on the price per kilo page.