Laboratory balances guide: how to choose and use a lab balance
Choose a laboratory balance by the smallest quantity you must weigh with confidence, not by the largest. Readability, repeatability and the minimum weight decide whether a result is valid; capacity only sets the upper limit.
Luminix Health is a European supplier and distributor of laboratory and hospital supplies, with 150.000+ products from established manufacturers and delivery across the EU in two to five days if in stock.
Part of the Luminix Health Laboratory Guide. Free download, no form: Laboratory Guide (PDF).
Last updated: 24 October 2026
Which type of balance do you need?
| Type | Typical readability | Typical capacity | Typical use |
|---|---|---|---|
| Micro / ultra-micro | 1 µg to 0.1 µg | Up to about 10 g | Filters, particulates, pharmaceutical micro-dosing |
| Semi-micro | 0.01 mg | Up to about 220 g | Reference standards, small sample masses |
| Analytical | 0.1 mg | Up to about 320 g | Standard and reagent preparation, gravimetry |
| Precision (top-loading) | 1 mg to 0.1 g | Up to about 30 kg | Media, buffers, formulation, quality control |
| Bench and floor scales | 1 g and coarser | Up to several tonnes | Goods-in, waste, large batches |
Typical values for guidance; always check the manufacturer's data sheet. Sources: see Official sources below.
Readability is not accuracy
Readability (d) is the smallest step on the display. The real limit is repeatability: the scatter of repeated weighings of the same load. A practical rule is that the sample mass should be well above the balance's minimum weight, which you derive from the repeatability measured on site and your required tolerance. Weighing 5 mg on an analytical balance with 0.1 mg readability gives a relative uncertainty that is often too high for a reference standard; a semi-micro balance is then the better choice.
Legal-for-trade and verified balances
When a mass determines a price, a medical treatment, a pharmacy preparation or a legal decision, the EU requires a verified non-automatic weighing instrument under Directive 2014/31/EU. These balances carry the CE marking plus the green M metrology sticker and an accuracy class: I (special), II (high), III (medium) or IIII (ordinary). Analytical balances are usually class I, precision balances class II. For routine research use, an ISO/IEC 17025 calibration certificate is usually what auditors ask for.
Placement, calibration and daily checks
- Place the balance on a stable, vibration-free weighing table, away from doors, air vents and direct sun.
- Let it warm up after power-on and level it with the built-in bubble.
- Use internal adjustment where available, and check daily or before each series with a calibrated test weight.
- Use a draft shield and antistatic measures for powders and plastics.
- Have the balance calibrated at a fixed interval, typically once a year, and keep the certificate with your quality records.
Frequently asked questions
How often should a laboratory balance be calibrated?
Most laboratories calibrate at least once a year under ISO/IEC 17025 and perform a short check with a test weight daily or before each weighing series. Increase the frequency after relocation, repair or heavy use.
What is the difference between calibration and adjustment?
Calibration compares the balance reading with a reference weight and documents the deviation. Adjustment changes the balance so that the reading matches the reference again. Internal adjustment does not replace an external calibration.
Do I need a verified (class I or II) balance?
Only when the weighing result has legal or commercial consequences, for example pharmacy preparations or selling by weight. For research and quality control, a calibrated balance with a certificate is usually enough.
Which balance do I need to weigh about 10 mg?
Choose by minimum weight, not by readability alone. The minimum weight follows from the repeatability measured on site (see Ph. Eur. 2.1.7 or USP <41>); for about 10 mg you typically need an analytical balance (0.1 mg) at least, and often a semi-micro balance (0.01 mg).
Do I need a draft shield or an anti-static kit?
A draft shield is needed from 1 mg readability and finer; analytical and semi-micro balances have one built in. Static on plastic vessels or dry powders causes drifting readings, especially at low humidity: an ionizer or anti-static kit solves this.
Internal or external calibration: which is better?
Internal adjustment uses a built-in motorised weight and corrects automatically after temperature changes. External adjustment uses certified weights. Either way, periodic calibration with traceable weights under your quality system remains necessary.
Order from the Luminix Health catalogue
Need a quote for several items or a framework order? Send your list to sales@luminixhealth.com.
