Scale Accuracy vs Precision: What the Numbers Really Mean

Scale specifications can be confusing. What does "0.1g accuracy" actually mean? Is "readability" the same as "accuracy"? This guide explains scale specs in plain language so you can choose the right scale and understand what your readings really tell you.

Quick Answer

Accuracy is how close to true weight; precision is how consistent. A 0.1g scale can detect differences of 0.1g (one-tenth gram). For flower, 0.1g works fine. For concentrates, you need 0.01g or 0.001g. Readability = smallest increment displayed. Accuracy = actual measurement reliability. They're related but not identical.

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Understanding Scale Specs

For statistical concepts in measurement accuracy, NIST Engineering Statistics Handbook provides technical guidance.

Readability (Resolution)

What it is: The smallest weight increment the scale displays.

Example:

• 0.1g readability shows: 1.0, 1.1, 1.2, etc.
• 0.01g readability shows: 1.00, 1.01, 1.02, etc.
• 0.001g readability shows: 1.000, 1.001, 1.002, etc.

Key point: This is what you SEE, not necessarily what's TRUE.

Accuracy

What it is: How close to the actual weight the reading is.

Example:

A scale might display 3.5g when the true weight is 3.48g or 3.52g. The accuracy tells you the expected deviation.

Common accuracy specs:

• "±0.1g" means reading could be off by up to 0.1g
• A 3.5g reading might actually be 3.4g to 3.6g

Precision (Repeatability)

What it is: How consistently the scale gives the same reading for the same item.

Good precision: Weigh same item 5 times, get 3.50g each time.

Poor precision: Weigh same item 5 times, get 3.48g, 3.52g, 3.49g, 3.51g, 3.50g.

The Relationship

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What Different Accuracies Mean in Practice

0.1g Accuracy (Pocket Scales)

What you can reliably measure:

• 1g and up with confidence
• 0.5g with reasonable accuracy
• Below 0.5g becomes unreliable

Best for:

• Verifying eighths, quarters, ounces
• General flower weighing
• Everyday use

Not great for:

• Single half-gram purchases
• Concentrates
• Precision dosing

Reading interpretation:

When scale shows 3.5g, actual weight is likely 3.4-3.6g.

0.01g Accuracy (Precision Pocket Scales)

What you can reliably measure:

• 0.1g and up with high confidence
• 0.05g with reasonable accuracy
• Better for small amounts

Best for:

• Verifying smaller purchases
• More accurate flower weighing
• Budget concentrate weighing
• Better edible dosing

Reading interpretation:

When scale shows 3.50g, actual weight is likely 3.48-3.52g.

0.001g Accuracy (Milligram Scales)

What you can reliably measure:

• 0.01g and up with high confidence
• 0.005g with reasonable accuracy
• Extreme precision

Best for:

• Concentrates
• Precise edible making
• Scientific accuracy
• Professional use

Reading interpretation:

When scale shows 3.500g, actual weight is likely 3.498-3.502g.

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Accuracy vs Precision Illustrated

Both Good (Ideal)

Readings: 3.50, 3.50, 3.50, 3.50, 3.50

True weight: 3.50g

Result: Perfect—accurate and precise.

Precise But Inaccurate

Readings: 3.55, 3.55, 3.55, 3.55, 3.55

True weight: 3.50g

Result: Consistently wrong. Needs calibration.

Accurate But Imprecise

Readings: 3.48, 3.52, 3.49, 3.51, 3.50

True weight: 3.50g

Result: Averages correct but individual readings vary. Environmental issue likely.

Neither (Bad Scale)

Readings: 3.45, 3.58, 3.42, 3.61, 3.49

True weight: 3.50g

Result: Unreliable. Replace or repair scale.

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Matching Accuracy to Purpose

For Cannabis Flower

Bottom line: 0.1g works for most flower purposes. 0.01g is better for small amounts.

For Concentrates

Bottom line: 0.001g is really the only appropriate accuracy for concentrates.

For Edibles

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Understanding Margin of Error

What ± Means

When specs say "±0.1g":

• Reading of 5.0g means actual could be 4.9-5.1g
• Reading of 3.5g means actual could be 3.4-3.6g

Error Compounds with Small Weights

At larger weights:

5.0g ± 0.1g = 2% potential error

At smaller weights:

0.5g ± 0.1g = 20% potential error

Lesson: Accuracy matters more for smaller amounts.

Why Cheap Scales Are Worse

Better scales:

• Tighter actual accuracy than spec
• More consistent
• Better at edges of range

Cheap scales:

• May not meet stated spec
• Worse at small weights
• More environmental sensitivity

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Testing Your Scale's Accuracy

Using Known Weights

Calibration weights (best):

• Known precise weight
• Use to verify and calibrate

Coins (adequate):

• US nickel = 5.00g
• US penny (post-1982) = 2.50g
• Stack for larger weights

Precision Test

1. Weigh same item 5 times

2. Record each reading

3. All same = good precision

4. Variation = precision issue

Accuracy Test

1. Weigh known weight (calibration weight or coins)

2. Compare to known value

3. Close = good accuracy

4. Off = needs calibration or replacement

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Improving Your Readings

Environmental Factors

For best accuracy:

• Level, stable surface
• Away from air currents
• Consistent temperature
• No vibrations

Usage Factors

For best accuracy:

• Calibrate regularly
• Fresh batteries
• Let scale warm up
• Don't rush readings

Scale Factors

For best accuracy:

• Quality brand
• Appropriate accuracy for task
• Proper maintenance
• Not exceeding capacity

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Quick Reference

Accuracy by Scale Type

When Readings Matter Most

• Verifying purchases: Need accuracy
• Consistent dosing: Need precision
• Making edibles: Need both
• Casual use: Either works

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Summary

Understanding scale specs helps you:

1. Choose right accuracy for your needs

2. Interpret readings correctly

3. Identify problems when they occur

4. Not overpay for unnecessary precision

For most cannabis flower use, 0.1g accuracy is sufficient. For concentrates or precision work, 0.001g is essential. Don't be fooled by extra decimal places—readability isn't the same as accuracy.

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This guide is for educational purposes. Always comply with local laws regarding cannabis.