Analytical Balance: Why 0.0001 g Doesn't Mean Accurate
Updated: Sep 28
An analytical balance reads to 0.0001 g (0.1 mg), but readability is not accuracy. Readability is just the smallest step the display shows. Accuracy depends on repeatability, linearity and where the balance sits.
The number that decides whether your result is valid is minimum weight: the smallest sample you can weigh within your required uncertainty.
Balance class | Readability | Typical capacity | Used for |
|---|---|---|---|
Micro balance | 0.001 mg (0.000001 g) | 2–10 g | Trace and forensic work |
Semi-micro balance | 0.01 mg (0.00001 g) | 50–100 g | Reference standards, potency assays |
Analytical balance | 0.1 mg (0.0001 g) | 100–300 g | The lab default |
Semi-analytical balance | 1 mg (0.001 g) | 100–300 g | Routine weighing with a draught shield |
Precision (top-loading) balance | 1 mg or 10 mg (0.001 g or 0.01 g) | 300 g–8 kg | Bulk reagents, media prep |
The short version
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Readability vs accuracy: what the specs mean
Readability is the smallest step the display shows; accuracy depends on repeatability and linearity, and repeatability is the best single guide.
Readability (d): the smallest increment displayed, 0.1 mg on an analytical balance.
Repeatability: the standard deviation from weighing the same object repeatedly. The best single guide to accuracy.
Linearity: how far readings deviate from a straight line across the range.
Eccentricity: error when the sample is off-centre. Centre the sample to avoid it.
Sensitivity drift: how readings change with temperature. Internal calibration corrects it.
“ Don't ask a supplier how many decimal places you need. Tell them your smallest routine sample weight. — LS Scientific |
Uncertainty: minimum weight and USP <41>
Minimum weight is the smallest sample you can weigh within your required uncertainty. Under USP <41>, twice the repeatability standard deviation divided by the sample mass must not exceed 0.10%.
Balance uncertainty is roughly fixed, so the smaller the sample, the bigger the percentage error. Weigh 100 mg with 0.1 mg uncertainty and you're at 0.1%. Weigh 5 mg and you're at 2%.
USP <41> requires uncertainty of no more than 0.10% of the amount weighed. If your method needs 20 mg of reference standard and your balance's minimum weight is 100 mg, it isn't compliant, whatever the display shows. For samples that small, look at a semi-micro or micro balance.
Prices: analytical balances in stock
Analytical balances cost from £1,040 (PR Series) to £4,399 (Explorer Plus EXP).
PR Series Analytical | £1,040 |
Pioneer Analytical | £1,420 |
Adventurer Analytical | £2,541 |
Explorer Analytical EXR | £3,829 |
Explorer Plus Analytical EXP | £4,399 |
PR Series Analytical: entry level for 100 mg+ samples. £1,040.25
Pioneer Analytical: £1,420.25
Adventurer Analytical: £2,541.25
Explorer Analytical EXR: £3,828.50
Explorer Plus Analytical EXP: top repeatability for regulated work. £4,398.50
All five read to 0.1 mg. What rises with price is repeatability (so lower minimum weight), draught shield design, calibration features and connectivity.
Get accurate results: calibration and siting
Keep an analytical balance accurate with regular internal calibration, a weekly check with a certified test weight, an accredited calibration once a year, and a draught-free, vibration-free site.
Internal calibration adjusts sensitivity automatically. Worth it where temperature varies or many people share the balance.
Check weekly with a certified OIML test weight, and record it.
Traceable calibration from an accredited lab once a year. That's what auditors ask for.
Site it on a heavy, vibration-free bench away from doors, air-con and fume cupboards.
Beat static on plastic vessels and dry powders with an anti-static ioniser.
Close the draught shield, centre the sample and wait for the stability indicator.
Our ISO 17025 calibration service covers traceable balance calibration on site. Measuring water rather than mass loss? See our Karl Fischer titration guide.
FAQ: analytical balances
What is the readability of an analytical balance?
0.1 mg, or 0.0001 g. A semi-analytical balance reads to 1 mg (0.001 g) and a semi-micro balance to 0.01 mg (0.00001 g).
Is readability the same as accuracy?
No. Readability is the smallest increment the display shows. Accuracy depends on repeatability, linearity, eccentricity and installation.
What is the uncertainty of an analytical balance?
It is mainly driven by repeatability. A good analytical balance might have repeatability of 0.05–0.1 mg, which sets its minimum weight under USP <41>.
What is minimum weight?
The smallest sample you can weigh while meeting your accuracy requirement. Under USP <41> it is about twice the repeatability divided by 0.001.
What is the difference between an analytical and a precision balance?
An analytical balance reads to 0.1 mg with a draught shield and 100–300 g capacity. A precision balance reads to 1 mg or 10 mg with capacity up to several kilograms.
How much does an analytical balance cost?
Between £1,040.25 and £4,398.50 in our range. All read to 0.1 mg; the price reflects repeatability, build and features.
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