Weighbridge gross, tare and net weight explained
Net weight = gross weight (the loaded lorry) − tare weight (the empty lorry). Weighing the same lorry both empty and loaded on the same trip gives the most reliable net weight.
The three weights
- Gross weight: the lorry with its load.
- Tare weight: the same lorry empty.
- Net weight: gross − tare, the weight of the material itself — the figure that goes into stock and on the bill.
The two-step weighing process
Material coming in (for example boulders to a crusher): the loaded lorry is weighed first (gross), unloads, and is weighed again empty (tare).
Material going out (dispatch to a customer): the empty lorry is weighed first (tare), loads, and is weighed again (gross).
Both weights go on one ticket with its own number, so the net weight can always be traced back.
Common mistakes
- Using an old stored tare: fuel, tools, spare tyres and body repairs change a lorry's empty weight.
- The lorry not fully on the platform, or the driver standing on it for one weighing and not the other.
- Typing the weight wrongly when copying from the weighbridge display.
- Tickets without numbers, or a ticket used for more than one load.
What a weighbridge ticket should show
- Ticket number, date and time of each weighing
- Vehicle number, material and the supplier or customer
- Gross, tare and net weight
- Who operated the weighbridge
How RockPro handles it
RockPro Crusher keeps two-step weighbridge tickets: the first weight is saved when the lorry arrives and the second when it returns. The net weight flows into the boulder inward or the dispatch, and from there into stock, the supplier's or customer's account and the GST invoice. Weights are typed from the weighbridge display.
Frequently asked questions
How is net weight calculated on a weighbridge?
Net weight is the gross weight of the loaded lorry minus the tare weight of the same lorry empty.
Is a lorry's tare weight fixed?
No. Fuel, tools, spare tyres and repairs change it, so weigh the lorry empty on each trip where you can instead of relying on a stored tare.
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