Best Pharmacy Balance: Class A Replacement and USP <1176> Guide

The best pharmacy balance for most compounding is the A&D FX-120i: 122 g x 0.001 g, on sale for $699.00 (regular $1,495.00), in stock. For legal-for-trade work, choose the NTEP A&D FX-120iN at $679.00.

Compounding pharmacies, veterinary pharmacies, hospital pharmacies and medical offices all need a balance they can trust down to the milligram. MNM Scales is an authorized A&D dealer and one of the largest scale distributors in the country, with over 30 years in business, and we sell, calibrate and service pharmacy scales and balances. This guide covers what USP expects, how to work out the smallest amount your balance can weigh accurately, and our picks.

From the Class A prescription balance to electronic balances

For decades, pharmacies used a torsion “Class A” prescription balance. USP now calls it a Class III prescription balance: it has a sensitivity requirement of 6 mg or less, and to keep errors at 5% or less you should not weigh less than 120 mg on it. USP <1176> states that pharmacies should have a Class III torsion balance or a superior balance, preferably electronic, and either a set of calibration weights or a balance with internal calibration.

An electronic balance replaces a Class A balance with faster, direct readings, a printer or PC output for records, and a much smaller minimum weighable quantity.

Minimum accurately weighable quantity (MAWQ)

USP <1176> defines the MAWQ as the smallest amount that produces no more than your accepted error. For an electronic balance, it is the balance linearity divided by the accepted error:

Balance	Linearity	MAWQ at 5% error	MAWQ at 0.5% error
Class III (Class A) torsion balance	Sensitivity requirement 6 mg	120 mg	1.2 g
A&D FX-120i, FZ-120i or FX-300i (0.001 g)	±0.002 g	40 mg	400 mg

For analytical balances, use the manufacturer’s linearity, or determine the minimum weight as described in USP <1251> and verify it at least annually and after moving or servicing the balance. If you weigh active ingredients below about 40 mg, an analytical balance such as the HR-250AZ or GX-124AN is the better tool.

Our picks: best pharmacy balance by job

Balance	Capacity x readability	Calibration	Best for
A&D FX-120i	122 g x 0.001 g	External (100 g or 50 g)	Most compounding: capsules, creams, suspensions
A&D FZ-120i	122 g x 0.001 g	Internal	Pharmacies that want one-touch internal calibration
A&D FX-300i	320 g x 0.001 g	External (300, 200, 100 or 50 g)	Larger containers and batches
A&D FX-323 Fortis	320 g x 0.001 g	External	Larger batches; backlit LCD
A&D HR-250AZ	252 g x 0.1 mg	Accepts 250, 200, 100 or 50 g weights	Potent ingredients and small quantities
A&D FX-104 Fortis	102 g x 0.1 mg	External	Compact analytical weighing
A&D GX-124AN Apollo	120 g x 0.1 mg	Internal	Analytical weighing with internal calibration; NTEP

The FX-i and FZ-i balances share A&D’s Super Hybrid Sensor, settle in about one second and include a breeze break; the FZ-120i adds a built-in calibration mass. The HR-250AZ has a 90 mm pan, a removable antistatic breeze break, a backlit LCD and RS-232C output. Comparing FX models? See our FX-120i vs FX-120iN vs FX-300i guide. If your pharmacy also sells product by weight, choose an NTEP model such as the FX-120iN (see what NTEP means).

Calibration weights for a pharmacy balance

USP expects either calibration weights or internal calibration. For a 0.001 g balance calibrated at 100 g, an ASTM Class 1 weight (0.25 mg tolerance) is a common choice, such as the A&D AD-100-10-20 Class 1 set (100 g, 10 g and 20 mg, with ISO/IEC 17025 certificate). The A&D 100 g weight fits the FX-120i for routine calibration (weights are sold separately, not included). See calibration weight classes explained for ASTM and OIML tolerances, browse all calibration weights, and follow our FX-120i calibration guide.

Daily checks and calibration service

• Place it right: a sturdy bench away from vents, doors and vibration; level it with the bubble.
• Warm it up: A&D recommends at least 30 minutes of warm-up on the FX-i and FZ-i.
• Check daily: weigh a check weight, compare with your SOP limits and log the result.
• Calibrate on schedule: at least once a year, and after a move, a drop or a failed check (see how often to calibrate).

MNM Scales is TDA licensed with registered technicians. We calibrate pharmacy balances with in-house or NIST-traceable certificates (which one does your inspector expect?), on-site for pharmacies, labs and medical offices in Houston and suburbs ($295 service call plus $2 per mile round trip, with calibration charged per balance), or by mail-in nationwide, usually in 1 to 3 business days:

Frequently asked questions

What balance do pharmacies need?

USP <1176> says pharmacies should have a Class III (formerly Class A) prescription balance or a superior balance, preferably electronic, plus calibration weights or internal calibration. Most compounding pharmacies choose a 0.001 g electronic balance such as the A&D FX-120i.

What replaced the Class A prescription balance?

USP now calls it a Class III prescription balance. Electronic balances that read 0.001 g, such as the A&D FX-120i or FZ-120i, are the usual modern choice.

What is the smallest amount I can weigh on a pharmacy balance?

USP <1176> uses the minimum accurately weighable quantity: linearity divided by accepted error. For a balance with plus or minus 0.002 g linearity at 5% error, that is 40 mg. A Class III torsion balance with a 6 mg sensitivity requirement gives 120 mg.

Do I need an analytical balance for compounding?

If you regularly weigh ingredients below about 40 mg, an analytical balance that reads 0.1 mg, such as the A&D HR-250AZ or GX-124AN, gives a smaller minimum weight.

Does a pharmacy balance need to be NTEP?

Compounding is not a sale by weight, so NTEP is usually not required for it. If you also sell product priced by weight, choose an NTEP model such as the A&D FX-120iN.

Do you calibrate pharmacy balances on-site?

Yes. On-site service for pharmacies, labs and medical offices in Houston and suburbs is a $295 service call plus $2 per mile round trip, plus calibration. Nationwide mail-in calibration usually takes 1 to 3 business days.