How to Calibrate an A&D FX-120i (Plus FX-123, FX-300i, FX-300iN and FX-323N)
Here is how to calibrate an A&D FX-120i (and the FX-123, FX-300i, FX-300iN and FX-323N) in a few minutes, or ship it to us for in-house calibration at $95.00 or NIST calibration at $395.00, nationwide by mail.
Quick version: level the balance, let it warm up for at least 30 minutes, and close the breeze break. Press and hold CAL until CAL out appears, then press PRINT with the pan empty. When the weight value appears, place your 100 g weight (50 g also works on 122 g models), press PRINT again, and remove it when the display reads end. NTEP “N” models are sealed and must be calibrated by a registered service technician. That’s a service we provide, by mail-in nationwide (usually 1 to 3 business days) or on site in the Houston area.
The A&D FX-120i is one of our best-selling balances. Reloaders, labs, jewelers and QC departments rely on it because it reads 0.001 g and settles in about a second. Like any milligram balance, it’s only as accurate as its last calibration. This guide walks through calibrating the FX-120i and its relatives, the FX-300i, the NTEP FX-300iN, and the newer Fortis FX-123 and FX-323N. The steps come from A&D’s instruction manuals, plus the setup tips our technicians use. Pairing your FX-120i with an AutoTrickler V4? See our FX-120i AutoTrickler setup guide for the exact scale settings. Still choosing a model? Compare the FX-120i, FX-120iN and FX-300i. For the keys, units, counting, function table and data output, see our FX-120i manual, explained.
Before you calibrate: setup is half the job
Most “my balance won’t calibrate” calls we get turn out to be setup problems. A&D’s manual is clear about the basics, and they matter even more at 0.001 g:
- Level it. Turn the leveling feet until the bubble sits in the center of the spirit level. Re-check every time the balance is moved.
- Warm it up. Plug in the AC adapter and leave the balance on for at least 30 minutes with nothing on the pan before you calibrate.
- Pick a solid, quiet spot. Use a sturdy table away from vents, heaters, air conditioners, direct sunlight and foot traffic. A&D recommends about 68 °F (20 °C) and roughly 50% relative humidity.
- Use the breeze break. A&D specifies the included breeze break during calibration on the FX-120i, 200i, 300i and 500i. Even a small air current shows up in the third decimal place.
- Watch out for static. In dry air (below about 45% RH), plastic parts and samples can hold a charge and make readings wander. Wipe the breeze-break panels with a slightly damp cloth, or use a static eliminator.
Which calibration weight does your model use?
| Model | Capacity × readability | Usable calibration weights (A&D) |
|---|---|---|
| A&D FX-120i | 122 g × 0.001 g | 100 g or 50 g |
| A&D FX-123 (Fortis) | 122 g × 0.001 g | 100 g or 50 g |
| A&D FX-300i | 320 g × 0.001 g | 300, 200, 100 or 50 g |
| A&D FX-300iN (NTEP) | 320 g × 0.001 g (e = 0.01 g) | 300, 200, 100 or 50 g (sealed, technician only) |
| A&D FX-323N (Fortis, NTEP) | 320 g × 0.001 g (e = 0.01 g) | 300, 200, 100 or 50 g (sealed, technician only) |
Using the largest weight your model accepts gives the best result across the range. The weight also has to be accurate enough for the balance. On a 0.001 g balance, use a weight whose tolerance is well under 1 mg. At 100 g, an ASTM Class 1 weight is held to ±0.25 mg and an OIML F1 weight to ±0.5 mg (see calibration weight classes explained for the full tables). Shop our calibration weights, such as the Rice Lake 100 g ASTM Class 1 weight or the 100 g weight for the FX-120i. Our FX-123 listing includes a 100 g calibration weight, and the FX-323N ships with a bonus 100 g test weight that MNM Scales tests in Texas.
Step by step: calibrating the FX-120i, FX-300i and other FX-i models
- Warm up. Connect the AC adapter and leave the balance on for at least 30 minutes with the pan empty and the breeze break in place.
- Enter calibration. Press and hold the CAL key until CAL out appears, then release it. The display shows CAL 0.
- (Optional) Change the weight value. To use a different weight from the list above, press SAMPLE. Use RE-ZERO (up) and MODE (down) to select it, then press PRINT to store it. If your certified weight has a known correction (for example 100.002 g), you can enter that exact value here. It stays in memory when the balance is unplugged.
- Zero point. Make sure the pan is empty and press PRINT. Don’t touch the bench while the balance measures zero.
- Span. The display shows the weight value. Place that weight in the center of the pan, close the breeze break and press PRINT.
- Finish. When end appears, remove the weight. If GLP output is turned on, the balance prints a calibration report and then returns to weighing mode.
- Verify. Place the weight back on the pan. A&D says the reading should be within ±2 digits of the weight value (for example 99.998 to 100.002 g). If it isn’t, check for drafts, vibration and a seated pan, then repeat.
Calibration test (no adjustment): if you only need a record that the balance is still accurate, which is common in GLP labs and pharmacies, turn on GLP output in the function table. Then press and hold CAL until CC out appears. The balance weighs your target weight and prints the result without changing its calibration.
Calibrating the Fortis FX-123 and FX-323
The Fortis series follows the same zero-then-span sequence with slightly different prompts. Warm the balance up for at least 30 minutes with the pan empty, then press and hold the CAL key for about 2 seconds. The display steps through the calibration options every 2 seconds or so. Release the key when the external-weight option appears. Then zero the empty pan, place the weight when prompted, and remove it when the balance finishes. A&D’s Fortis quick-start guide shows the key icons for each step. Fortis models accept 50 g or 100 g weights at 122 g capacity and up to 300 g at 320 g capacity.
NTEP models (FX-120iN, FX-300iN, FX-323N): why you can’t press CAL
On legal-for-trade versions, external calibration is locked. The calibration switch sits behind a sealed panel, and A&D’s legal-for-trade supplement states that calibration and sealing must be done by a weights and measures official or an authorized service agency. Breaking the seal yourself takes the balance out of compliance. Dispensaries, jewelers and other businesses that sell by weight should have a registered technician do it.
Our TDA-registered technicians calibrate and re-seal NTEP balances in our Houston-area shop, by mail-in from anywhere in the U.S. (usually 1 to 3 business days), or on site across the Houston area and suburbs. Service in Dallas, Austin and San Antonio is available on request.
Troubleshooting: when calibration fails or readings drift
- Error or “out of range” during calibration: the weight value set in the balance doesn’t match the weight on the pan, or the balance wasn’t zeroed with an empty pan. Check the stored weight value (step 3) and try again. For CAL E, -E and other codes, see the FX-120i error codes below and scale error codes explained.
- Last digit won’t settle: look for drafts, vibration, static or a warm sample. A&D notes that a sample warmer than the room reads light and a cooler one reads heavy. Let samples reach room temperature.
- Weighing steel or magnetic parts: the FX sensor uses a strong magnet. Use the built-in underhook to hang magnetic items below the balance.
- Reads correctly at 100 g but not at 10 g: that points to linearity rather than span calibration. Call us and we’ll check the balance at several points across its range.
How to factory reset (initialize) an FX-120i
If settings were changed by mistake and the balance no longer behaves as expected, A&D’s FX-i manual (section 8-2, FX-i instruction manual) describes an initialize function that returns the balance to factory settings. It resets the calibration data, the function table, the counting unit mass and percent reference mass, the external calibration weight value, the function switch settings and the statistical data.
- Press ON:OFF to turn the display off.
- While holding PRINT and SAMPLE, press ON:OFF. The display shows p5.
- Press SAMPLE to display Clr.
- Press PRINT. To cancel at this point, press CAL.
- Press RE-ZERO.
- Press PRINT to initialize. The balance returns to weighing mode on its own.
Calibrate the balance right after a reset, because the calibration data is cleared too. The FX-120i uses a 100 g weight: the A&D 100 g calibration weight is $59.00, or step up to the Rice Lake 100 g ASTM Class 1 weight at $148.00 (prices checked October 30, 2026). Reloaders: a reset also clears the function table, so re-enter the settings in our FX-120i AutoTrickler setup guide.
On an NTEP model (FX-120iN, FX-300iN, FX-323N), call us before you initialize: recalibrating a sealed legal-for-trade balance is a job for a registered service technician, and our TDA-registered technicians can do it by mail-in or on site.
FX-120i error codes at a glance
| Display | Meaning (A&D manual) | What to do |
|---|---|---|
| E | Overload | Remove the sample. |
| -E | Weighing pan error: the value is too light | Check the pan is installed properly, then calibrate. |
| CAL E / -CAL E | Calibration weight too heavy / too light | Check the pan and the stored weight value; press CAL to return to weighing. |
| Lo | Counting or percent sample too light | Use a heavier sample. |
| Error 1 | Stability error | Remove drafts, vibration and static; press CAL. |
For the full list across brands, see scale error codes explained.
How often should you calibrate?
A&D recommends calibrating when the balance is first installed, any time it’s moved, when the room environment changes, and periodically. For critical work, check it before each use. A common practice in pharmacies, labs and dispensaries is a quick daily or weekly check with your own weight, plus certified calibration at least once a year or as often as your auditor or state inspector requires.
Let MNM Scales calibrate it for you
All the balances in this guide have a capacity of 2.2 kg or less, so they fall in our first calibration tier. Add calibration to a new balance order and it ships calibrated, or send in the balance you already have:
- In-house calibration with certificate (NIST-tested weights): $95. Add $95 calibration to cart
- NIST calibration with NIST-traceable certificate: $395. For audits, pharmacies, dispensaries and labs. Add $395 NIST calibration to cart
- Mail-in calibration, nationwide, with in-house and NIST calibration: usually 1 to 3 business days in our shop. Request mail-in calibration
- On-site service across the Houston area and suburbs: $295 service call plus $2 per mile round trip. Same-day and emergency visits depend on availability, so call us. See our scale services
MNM Scales has been in business for over 30 years. We’re an authorized A&D dealer and one of the largest scale distributors in the country. Customers tell us they come back because a real person answers the phone and knows these balances, orders ship fast from our Texas shop, and we beat competitor pricing when they call. Replacing an older FX-300iN? Read our FX-300iN vs FX-323N guide.
Frequently asked questions
How do I calibrate my A&D FX-120i?
Warm it up for 30 minutes with the pan empty. Press and hold CAL until “CAL out” appears and press PRINT to set zero. When prompted, place the 100 g (or 50 g) weight and press PRINT, then remove the weight when the display reads “end”. Re-weigh the weight to confirm the reading is within ±2 digits.
What calibration weight does the FX-120i use?
A&D lists 100 g or 50 g for the FX-120i and the Fortis FX-123. Use a weight with a tolerance well under 1 mg, such as ASTM Class 1 (±0.25 mg at 100 g) or OIML F1 (±0.5 mg at 100 g).
Can I calibrate a milligram balance with coins?
We don’t recommend it. Coin weights vary with wear and manufacturing tolerance and have no certificate, so they can’t calibrate a 0.001 g balance accurately. Use a certified weight, or let us calibrate the balance with NIST-tested weights.
Can I calibrate my FX-300iN or FX-323N myself?
Calibration on NTEP legal-for-trade models is locked behind a sealed panel. A&D states that a weights and measures official or authorized service agency must calibrate and seal them. MNM Scales is TDA licensed with registered technicians and handles this by mail-in or on site.
How long does mail-in calibration take?
Mail-in calibration is available nationwide, with in-house calibration and NIST calibration and usually takes 1 to 3 business days in our shop, plus shipping time.
Why won’t the last digit on my FX-120i settle?
Usually because of drafts, vibration, static or a sample that’s warmer or cooler than the room. Close the breeze break, move the balance away from vents, ground it, keep humidity above about 45%, and let samples reach room temperature.
How do I factory reset an A&D FX-120i?
Turn the display off, hold PRINT and SAMPLE and press ON:OFF until p5 appears, press SAMPLE for Clr, then PRINT, RE-ZERO and PRINT again. The balance returns to factory settings and goes back to weighing mode.
Does a factory reset erase the FX-120i calibration?
Yes. Initializing clears the calibration data along with the function table and other settings, so calibrate the balance with a 100 g weight right after a reset. On NTEP models, call us first.
What does CAL E mean on an FX-120i?
CAL E means the calibration weight read too heavy and -CAL E too light. Check that the pan is installed properly and that the stored weight value matches your weight, then press CAL and try again.