Free Tablet Friability Calculator and N to kgf Converter
Two small tools for tablet quality-control work: a friability calculator that checks your result against the common 1.0% limit, and a converter between newtons (N), kilograms-force (kgf) and pounds-force (lbf) for tablet hardness readings. Both run in your browser; nothing you enter is stored or sent anywhere.
Tablet Friability Calculator
Formula: friability (% weight loss) = (W1 − W2) ÷ W1 × 100.
Worked example: W1 = 6.500 g and W2 = 6.470 g give (6.500 − 6.470) ÷ 6.500 × 100 = 0.46%.
Conditions assumed by the 1.0% comparison: the standard compendial method (USP <1216>, Ph. Eur. 2.9.7, ChP 0923), 100 rotations at 25 rpm, tablets de-dusted before and after the run. Under USP <1216>, a sample with cracked, split or broken tablets after tumbling fails regardless of the weight loss. Your own product specification may set a different limit; use it if it does.
Newton ↔ Kilogram-force ↔ Pound-force Converter
1 kgf = 9.80665 N (exact, by definition) and 1 lbf = 4.4482216 N. Tablet hardness is a crushing force, so a reading in kgf is the same quantity as the reading in N divided by 9.80665. Hardness readings are sometimes given in kp (kilopond); 1 kp = 1 kgf.
| N | kgf | lbf |
|---|---|---|
| 10 | 1.02 | 2.25 |
| 50 | 5.10 | 11.24 |
| 100 | 10.20 | 22.48 |
| 200 | 20.39 | 44.96 |
| 350 | 35.69 | 78.68 |
The 10–350 N row range is the force range of our YPD-350N hardness tester, which lets the operator switch the display between N and kg, so historical kgf records can be compared with newton readings directly.
Frequently Asked Questions
What is tablet friability?
Friability is the tendency of a tablet to lose material by abrasion and shock. In the compendial test, a weighed sample is tumbled in a rotating drum, de-dusted and weighed again; the percentage weight loss is the friability.
How many rotations does the friability test use?
The standard method uses 100 rotations at 25 rpm, which takes four minutes.
What is the usual friability limit?
A mean weight loss of not more than 1.0% is the common acceptance criterion in the harmonised compendial method. Check your own product specification and the current compendial text for the limit that applies to you.
Why do hardness testers show kgf or N?
Hardness is the force needed to crush a tablet. Older instruments and records often use kilograms-force; the SI unit is the newton. The converter above translates between them.
Related
For the full method, sample sizes and common execution errors, see our tablet friability testing guide. Instruments: the CJY-300E tablet friability tester and the YPD-350N tablet hardness tester. Questions about your own test setup can be sent through our contact page.