To calibrate a postal scale: clean the platform, power on and wait 60 seconds, press Tare to zero, then hold MODE or CAL until the display shows the required calibration weight. Place the exact weight in the centre of the platform, wait for PASS, then verify with a known object. No calibration weights? Use US nickels — each weighs exactly 5.000g. Note: Dymo M-series scales have no user calibration mode — see the brand table below.
Why postal scales lose calibration
A postal scale has one job: tell you the correct weight so you pay the right postage. When it drifts, you either overpay on every package or — worse — underpay and have mail returned. For a business sending 50 packages a day, even a small consistent error adds up fast.
Postal scales are generally more forgiving than jewelry scales, but they still drift. The most common culprits are low battery, being moved from one surface to another, and vibration from nearby printers or sorting equipment. Postal scales used near label printers are particularly vulnerable — the motor vibration transmits through the desk into the load cell.
Most postal scales are accurate to ±0.1% of the measured value per NIST guidelines for commercial scales. A 10lb package should read within 0.16oz of its true weight. If yours is consistently off by more than that, calibration — or a battery change — is overdue.
What you need before you start
- A hard, flat surface. Away from printers, label dispensers, and anything that vibrates. A rubber mat on the desk helps absorb low-level vibration.
- Fresh batteries. Low battery is the number one cause of postal scale drift. Replace them before calibrating — not after.
- The correct calibration weight. Most postal scales calibrate at their maximum capacity — a 10lb scale needs a 10lb weight. Check the bottom of the scale or the manual. For smaller postal scales, 100g or 200g is common. See our guide to calibration weights for what to buy.
- Your scale’s manual. Button sequences vary significantly between postal scale brands. Dymo scales in particular have no user calibration — knowing this upfront saves frustration.
How many coins do you need?
No calibration weight? US nickels weigh exactly 5.000g each. Most small postal scales (up to 500g / ~1lb) can be calibrated with nickels. Larger scales rated in pounds are trickier — you’d need 91 nickels for a 1lb calibration (453.6g). At that point, a proper calibration weight set makes more sense.
Coin calibration weight calculator
Enter your scale’s required calibration weight in grams. Not sure? Check the bottom of your scale.
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US nickels
Note: For postal scales rated in pounds, convert first: 1 lb = 453.592g. Large calibration weights are usually cheaper than stacking 90+ nickels.
| Coin | Weight (grams) | Good for calibration? |
|---|---|---|
| Nickel (5¢) | 5.000g | ✓ Best choice for gram-rated scales |
| Penny (post-1983) | 2.500g | ✓ Good for odd targets |
| Quarter (25¢) | 5.670g | △ Awkward denominations |
Many postal scales display in ounces or pounds, not grams. Your calibration weight still needs to match the scale’s required weight. Check whether your scale’s manual specifies the calibration weight in grams, ounces, or pounds — and convert accordingly before using the calculator above. 1 oz = 28.35g.
Step-by-step calibration
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Clean the platformWipe the weighing platform with a dry cloth. Check underneath for debris. Even a staple or paper scrap trapped under the platform can add a consistent false reading.
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Install fresh batteries and power onReplace the batteries if they haven’t been changed in 6 months. Turn the scale on. Let it sit undisturbed for 60 seconds. Don’t place it near a running printer or label dispenser during this warm-up.
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Zero the scaleNothing on the platform. Press Tare or Zero. Wait for a stable 0.0 reading. Some postal scales reset to 0.00 oz or 0.0 lb — that’s fine. If it won’t hold zero, check for vibration sources nearby before continuing.
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Enter calibration modeSee the brand table below for your exact sequence. Most scales: hold
MODEorCALfor 3–5 seconds untilCALappears. Stamps.com scales: holdONthen pressCALthree times. If nothing happens, check whether your scale has a user calibration mode at all — Dymo M-series do not. -
Place the calibration weightPlace the exact required weight gently in the centre of the platform. Do not bump the scale or desk while waiting. The display will stabilise and either auto-confirm or wait for you to press a button.
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Confirm and verifyWait for
PASSor automatic return to weighing mode. Remove the weight and re-zero. Verify by weighing a known object — a sealed 100g bag of sugar, a US nickel (5.000g), or a letter with a known weight. If the reading is off, repeat from Step 2.
25 US dimes weigh exactly 2 ounces (56.7g total). If your postal scale shows 2.0 oz when you place 25 clean dimes on it, calibration is good. This takes 10 seconds and requires no calibration weights.
Button sequences by brand
| Brand / model | Calibration sequence | Display shows | Required weight |
|---|---|---|---|
| Stamps.com scale | Turn off → hold ON → press CAL three times → press ON → hold CAL → press ON |
CAL → place 10lb weight → confirm |
10 lb |
| USPS / generic postal scale | Hold MODE 3–5 s or hold TARE + ON/OFF simultaneously |
CAL → flashes required weight |
Max capacity |
| American Weigh Scales (AWS) | Press ON/OFF → hold MODE 3–5 s |
CAL → flashes weight → PASS |
Usually 200g or max capacity |
| Dymo M3, M5, M10, M25 | No user calibration available. Factory calibrated only. | N/A | N/A — contact Dymo support |
| Accuteck / generic USB postal | Hold CAL while powering on |
CAL → place weight → PASS |
Check base of scale |
| Salter Brecknell | Hold ZERO + ON simultaneously |
CAL → place weight → stabilise |
Max capacity |
Can’t find your brand? Search: [your brand] [model number] calibration PDF — the manufacturer’s PDF is more reliable than any third-party guide.
Is your postal scale accurate?
Enter your known weight and what the scale displayed. The tool gives you an instant pass/fail result.
Scale accuracy test
Good test objects: a US nickel (5.000g), a known-weight letter, or a sealed bag of sugar with the net weight printed on the packet.
For NIST commercial scale standards, a postal scale should read within ±0.1% of the true weight. Use the full accuracy tester tool → for more detail.
Troubleshooting
| Symptom | Most likely cause | Fix |
|---|---|---|
| Reads consistently high or low | Calibration drift | Calibrate using the steps above |
| Reading jumps around | Vibration from nearby printer / equipment | Move scale away from printer; place on rubber mat |
Shows Lo or battery icon |
Low battery | Replace batteries — do this before anything else |
Shows ERR or OVER |
Overloaded — package exceeds max capacity | Remove package immediately; check scale’s max capacity |
| Won’t hold zero — drifts up | Debris under the platform or uneven surface | Clean under platform; move to a flat, hard surface |
| Calibration completes but still reads wrong | Calibration weight was inaccurate | Repeat with verified weights or fresh, clean coins |
| Dymo scale reading incorrectly | No user calibration available on Dymo M-series | Replace batteries; if still wrong, contact Dymo support — may qualify for warranty replacement |
How often to calibrate
For a home office sending occasional packages, calibrate every 3–6 months and whenever the scale is moved.
For a business shipping daily, calibrate monthly and spot-check weekly with a known-weight object.
Always calibrate after:
- Moving the scale to a new location or surface
- Replacing batteries
- Noticing packages being returned for insufficient postage
- A drop or knock
- Readings that seem inconsistent or don’t match a known weight