Last updated: August 2026 · Reviewed by Right Weigh Scale — California Registered Service Agency (RSA #3421)
In California, county Weights & Measures inspects and seals commercial scales annually, and most counties require annual registration of each commercial device. The state does not mandate a fixed service-calibration interval, but industry best practice is to recalibrate every 6 to 12 months — and re-verification is required after any repair, adjustment, or relocation that affects accuracy. The scale owner is legally responsible for keeping the device accurate between inspections.
Schedule calibration → · Call (510) 315-8883
The short answer
| Trigger | Frequency / requirement |
|---|---|
| County inspection & sealing | Annually (by your county Weights & Measures) |
| County registration | Annually in most counties |
| Recommended recalibration | Every 6–12 months (best practice) |
| High-use / harsh-environment scales | Often every ~6 months |
| After repair, adjustment, or relocation | Re-verification required before commercial use |
| Owner responsibility | Maintain accuracy at all times between inspections |
What California actually requires
California regulates commercial weighing devices through the Division of Measurement Standards (DMS), part of the CDFA, with enforcement at the county Weights & Measures level. Two things are mandatory for any scale used in commerce:
- Annual inspection and sealing. County inspectors test commercial scales and apply a dated approval seal showing when the device was last inspected.
- Annual registration (in most counties). A local ordinance typically requires each commercial device to be registered with the county each year.
What California does not do is mandate that a service company recalibrate your scale on a set schedule. Instead, the law makes the owner responsible for the scale’s accuracy at all times. A scale that passes inspection in January can still drift out of tolerance by summer — and if it does, the owner is liable, not the inspector.
County rules vary. Confirm specifics with your local County Weights & Measures office; we can help you understand what applies to your equipment and location.
Why best practice is every 6–12 months
Because owners carry the accuracy obligation between annual inspections, relying on the once-a-year county check alone is risky. Most scale professionals recommend recalibration every 6 to 12 months, with the interval driven by:
- Usage volume — a high-throughput retail or recycling scale drifts faster than a low-use one.
- Environment — outdoor truck scales, dusty recycling yards, and wash-down food areas stress equipment.
- Load severity — scales regularly loaded near capacity wear faster.
- Cost of error — high-value transactions (precious metals, cannabis, freight) make even small drift expensive.
A scale that over-reads gives product away on every transaction; one that under-reads risks customer disputes and citations. Regular calibration is cheaper than either failure mode.
When re-verification is always required
Independent of the annual cycle, a legal-for-trade scale must be re-verified and re-sealed before returning to commercial use after:
- Repair of any kind
- Adjustment that could change readings
- Relocation or reinstallation
In California, that re-seal must be placed by a Registered Service Agency (RSA). Right Weigh Scale holds RSA #3421 and is authorized to recalibrate and re-seal your scale legal-for-trade across the Bay Area and Northern California.
Calibration vs. county inspection — what's the difference?
| County inspection | Service calibration (by an RSA) | |
|---|---|---|
| Who | County Weights & Measures | A Registered Service Agency (e.g., RSA #3421) |
| How often | Annually | Every 6–12 months (best practice) + after repair/move |
| Purpose | Verify & seal for legal compliance | Adjust to traceable accuracy + re-seal |
| Result | Pass/fail + dated seal | NIST-traceable calibration + documentation |
The annual county seal proves your scale passed on inspection day. Routine RSA calibration keeps it accurate the rest of the year — and ensures it passes the next inspection.
How Right Weigh Scale keeps you compliant
- California Registered Service Agency (RSA #3421) — authorized to recalibrate and re-seal legal-for-trade.
- ISO/IEC 17025 accredited, NIST-traceable calibration up to 20,000 lb, with documentation.
- On-site across the Bay Area & Northern California — minimal downtime.
- Annual recalibration maintenance contracts — we track your interval and schedule service so you never miss a cycle or fail an inspection.
Schedule calibration → · Call (510) 315-8883 ·
Frequently asked questions
Is annual calibration required by law in California? California requires annual county inspection and (in most counties) annual registration of commercial scales, but it does not mandate a fixed service-calibration interval. The owner is legally responsible for accuracy at all times, which is why best practice is recalibration every 6 to 12 months.
How often should high-use scales be calibrated? Heavily used or harsh-environment scales — recycling, food processing, outdoor truck scales — commonly need recalibration every 6 months because they drift faster. Matching the interval to usage and environment prevents failed inspections and inaccurate transactions.
Do I need to recalibrate after repairing a scale? Yes. A legal-for-trade scale must be re-verified and re-sealed before returning to commercial use after any repair, adjustment, or relocation. In California, only a Registered Service Agency, such as Right Weigh Scale (RSA #3421), can place that seal.
Who is responsible if my scale is inaccurate between inspections? The scale owner is legally responsible for keeping a commercial scale accurate at all times, not just on inspection day. Routine calibration every 6 to 12 months protects you from liability, customer disputes, and county citations.
