Can I rely on the calculator's result as the weight my carrier will officially charge?
Treat it as a careful estimate, not an official figure. The calculator works exactly from the dimensions, weight and divisor you enter, but the carrier bills on its own measurement of the parcel, its own divisor for the service and its own rounding rules. The result is useful for catching surprises before you ship and checking an invoice afterwards, not as a guaranteed charge, and it shows no prices at all.
What the tool guarantees, and what it does not
- It guarantees: the maths is right for the numbers you entered, and unit conversions are exact.
- It does not guarantee: that your dimensions match the courier staff's tape, that the divisor you chose is your service's, or how your carrier rounds.
- It does not know: any price, fee or discount on your account, and it connects to no carrier.
What one centimetre changes
To see how sensitive the figure is, I ran a 4 kg carton with 5000 as an example divisor:
- Your measurement, 45 × 35 × 25 cm: chargeable weight 7.88 kg.
- If the carrier measures 1 cm more each way, 46 × 36 × 26 cm: 8.61 kg.
One centimetre on each side added nearly three quarters of a kilo, before any carrier rounding. An overfilled carton that bulges, tape wrapped around it, or a quick measurement with a slanted tape all add that centimetre easily.
Uses where you can rely on the figure
- Comparing carton sizes before buying them in bulk: the comparison holds because every option is calculated the same way.
- Spotting a light, bulky parcel before you quote a customer for shipping.
- Checking a line on a carrier invoice: if it differs a lot from your figure, ask which dimensions were recorded.
Bringing your estimate closer to the invoice
- Measure the carton once packed and sealed, at its widest points, and enter the figures in the Volumetric shipping-weight calculator.
- Use the divisor written in your contract or service page, not one from memory.
- Add a centimetre to each side if you want a safety margin, and apply your carrier's rounding rule to the result.
- If you invoice the customer for shipping with the Basic invoice generator, charge the amount you will actually pay, not the estimated weight.
When you ship the same sizes often, compare your estimates with several real invoices. After a month you will know how much your carrier usually adds, and your estimate gets closer without ever becoming an official figure.
Common questions
Can I dispute an invoice with the calculator's result?
It helps you ask the question, but the carrier's measurement and terms decide. Ask them for the dimensions they recorded.
Does the tool keep my past calculations?
No. Use Copy result and keep the text with the order if you want to refer back to it.
Why does the tool show no shipping prices?
Prices differ between carriers, accounts and services, and any price it showed could be wrong for you.