Small Parts Counting Scale: How to Count Screws, Washers and Electronic Parts Accurately
Reviewed by MNM Scales technicians · Updated October 30, 2026 · Prices checked October 30, 2026
Short answer: a small parts counting scale must have a minimum unit weight far below your lightest part and enough internal resolution to tell one piece from the next. For screws, washers, rivets and electronic components, we recommend the A&D FC-500i ($874.00), which counts parts down to 0.0005 g in fine mode. For the tiniest parts, step up to the A&D FC-500Si ($1,188.00, down to 0.00005 g). For bins of hardware up to 30 lb, the A&D HC-15Ki ($519.00) or Brecknell B140-30 ($299.00) keep the cost down.
Counting small parts by weight is fast, but only if the scale can resolve a single piece. Get it wrong and a bag of 2,000 washers comes out 40 short. MNM Scales has supplied, calibrated and repaired scales for over 30 years, and from our Cypress, Texas shop we set up counting scales for stockrooms, fastener and hardware suppliers, electronics assembly, kitting and shipping. This guide is about the hard case: light parts. For counting scales in general, read our counting scale buying guide.
Why small parts are hard to count by weight
A counting scale weighs a sample, works out the average piece weight, then divides the total weight by it. With small parts, three things push the count off:
- Sample error. If the piece weight is learned from 10 light parts, any error in that tiny sample weight is multiplied across the whole batch. Example: ten 0.25 g washers weigh 2.5 g. On a scale that only resolved its displayed 0.05 g, that is a 2% error in the piece weight, or about 40 pieces on a 2,000-piece count.
- Total-weight error. The count error equals the weight error divided by the piece weight. With 0.25 g washers, a 0.5 g error in the total is already 2 pieces.
- Part-to-part variation. Stamped, molded and plated parts vary in weight. A bigger sample averages out the variation; one unusual part in a 10-piece sample skews everything.
Counting scales fight this with internal resolution far finer than the display. The A&D FC-i series resolves 1/1,000,000 internally, so the 500 g FC-500i works with steps of 0.0005 g even though it displays 0.05 g. That matches its 0.0005 g fine-mode minimum unit weight. A&D’s ACAI (Automatic Counting Accuracy Improvement) then recalculates the piece weight as you add more parts, so the sample error shrinks as you go.
Match the scale to your lightest part
Start with the lightest part you count, not the heaviest. Weigh 100 of them on any scale and divide by 100, then pick a model whose minimum unit weight is well below that number:
| Lightest piece weight | Typical parts | Scale to look at |
|---|---|---|
| Under 0.01 g | Small SMD components, tiny springs, labels | A&D FC-500Si (0.00005 g in fine mode) |
| 0.01 to 0.1 g | Small washers, tiny screws, resistors, pins | A&D FC-500i (0.0005 g in fine mode) |
| 0.1 to 1 g in larger trays | Machine screws, nuts, rivets, connectors | A&D FC-2000i, A&D GC-3K or A&D HC-3Ki |
| Over 1 g, bins up to 30 lb | Bolts, fittings, molded parts, hardware kits | A&D HC-15Ki or Brecknell B140-30 |
Small parts counting scales compared
| Scale | Capacity x readability | Minimum unit weight (normal / fine) | Memory and power | Calibration tier | Price |
|---|---|---|---|---|---|
| A&D FC-500Si | 500 g x 0.02 g | 0.001 g / 0.00005 g | 500 IDs, 5 x 5 in pan | Up to 2.2 kg | $1,188.00 |
| A&D FC-500i | 500 g x 0.05 g | 0.01 g / 0.0005 g | 500 IDs | Up to 2.2 kg | $874.00 |
| A&D FC-2000i | 2 kg x 0.2 g | 0.04 g / 0.002 g | 500 IDs | Up to 2.2 kg | $874.00 |
| A&D FC-5000i | 5 kg x 0.5 g | 0.1 g / 0.005 g | 500 IDs | 2.2 to 6.2 kg | $874.00 |
| A&D GC-3K | 3 kg x 0.5 g | 0.1 g / 0.005 g | 1,000 items (microSD) | 2.2 to 6.2 kg | $798.00 |
| A&D HC-3Ki | 6 lb x 0.001 lb (3 kg x 0.5 g) | 0.1 g / 0.005 g | 99 IDs | 2.2 to 6.2 kg | $515.00 |
| A&D HC-15Ki | 30 lb x 0.005 lb (15 kg x 2 g) | 0.4 g / 0.02 g | 99 IDs | 6.2 to 35 kg | $519.00 |
| Brecknell B140-12 | 12 lb x 0.0005 lb (6 kg x 0.2 g) | 0.05 g | Stored part numbers, battery | 2.2 to 6.2 kg | $297.99 |
| Brecknell B140-30 | 30 lb x 0.001 lb (15 kg x 0.5 g) | 0.1 g | Stored part numbers, battery | 6.2 to 35 kg | $299.00 |
| OHAUS RC31P1502 (NTEP) | 3 lb x 0.0001 lb (1.5 kg x 0.05 g) | NTEP Class III, e = 0.001 lb (0.5 g) | 30-item library, battery | Up to 2.2 kg | $741.00 |
| OHAUS RC31P3 (NTEP) | 6 lb x 0.0002 lb (3 kg x 0.1 g) | NTEP Class III, e = 0.002 lb (1 g) | 30-item library, battery | 2.2 to 6.2 kg | $741.00 |
Our picks for small parts
Best for most small parts: A&D FC-500i
The FC-500i ($874.00 (regular $1,680.00)) is the scale we reach for when parts weigh well under a gram. It counts down to 0.0005 g per piece in fine mode, stores 500 IDs with unit weight, tare and limits, and has ACAI and an RS-232C port for a printer or PC. A rechargeable battery and a second weighing platform for bulk counting are available as options (not included).
For the tiniest parts: A&D FC-500Si
The FC-500Si ($1,188.00 (regular $2,315.00)) uses A&D’s Super Hybrid Sensor with 5 million internal counts, 0.02 g readability and a 5 x 5 in pan, for SMD components, small springs and labels down to 0.00005 g each in fine mode.
View price and stock: $1,188.00
For kitting stations: A&D GC-3K
The GC-3K ($798.00 (regular $1,225.00)) stores 1,000 items on a microSD card, so each part number keeps its piece weight and tare. It runs on AC, USB or a mobile battery, and A&D’s free WinCT-Count software logs counts to a PC.
Value pick: A&D HC-3Ki
The HC-3Ki ($515.00 (regular $930.00)) gives A&D counting with ACAI and 99 IDs at a lower price, with 6 lb x 0.001 lb capacity and a 0.005 g fine-mode minimum unit weight. The battery and RS-232C interface are options (not included).
Budget with battery: Brecknell B140-12 and B140-30
The Brecknell B140-12 ($297.99 (regular $410.00)) counts parts down to 0.05 g on a 12 lb platform, and the B140-30 ($299.00 (regular $430.00)) handles 30 lb bins with a 0.1 g minimum piece weight. Both have a built-in rechargeable battery for counting on the shelf.
When the count sets a price: OHAUS Ranger Count 3000
If you sell parts by count or weight, choose an NTEP model. The OHAUS RC31P1502 ($741.00 (regular $1,252.00)) and RC31P3 ($741.00 (regular $1,252.00)) are NTEP Class III with a 30-item library, check-counting lights and up to 210 hours of battery life; for 30 lb bins there is the RC31P15 ($741.00 (regular $1,252.00)).
How to count small parts accurately, step by step
- Set up the scale. Level it on a firm bench away from fans, doors and vibration, and let it warm up before the first count.
- Tare the container. Put the empty tray, cup or bin on the pan and press tare.
- Choose a bigger sample for light parts. Use 25, 50 or 100 pieces instead of 10. Brecknell recommends a sample weight of at least 0.1% of capacity (6 g on a 6 kg scale); A&D scales prompt for more pieces when the sample is too light.
- Let ACAI work. On A&D scales, add a few more pieces (more than three) after sampling and wait until the ACAI mark stops blinking. Each pass refines the piece weight.
- Count the batch by pouring in the rest. Keep parts inside the pan area and let the reading settle.
- Re-sample each new lot. Piece weight changes between suppliers, plating runs and production lots.
- Spot-check. Hand count a small batch now and then, and check the scale with a known weight. Our free scale tolerance calculator shows how much a reading may vary.
Seeing a code instead of a count, such as Lo, LACK or Err 9? It usually means the sample or piece weight is too light. Our scale error codes guide lists what each code means.
Small parts counting scale buying checklist
- ☐ The minimum unit weight (in the mode you will use) is well below your lightest part.
- ☐ Capacity covers your largest batch plus the container.
- ☐ ACAI or a similar accuracy feature, and sample sizes of 25, 50 and 100.
- ☐ Enough memory for your part numbers (99, 500 or 1,000 IDs).
- ☐ RS-232C or USB output if counts go to a printer, PC or inventory system (cables and printers not included). See how to connect a scale to a computer.
- ☐ A battery if you count on the shelf or in receiving.
- ☐ An NTEP model if the count or weight is used to charge a customer.
- ☐ A plan for calibration and a calibration weight to check it (calibration weights, sold separately).
Do you need a legal-for-trade counting scale?
Counting parts for your own inventory, kitting or production does not set a price for a customer. Selling parts by count or by weight does, and then the scale is a commercial device. TDA does not require an NTEP certificate for every device, but the scale must meet NIST Handbook 44 and suit its use; some scales do need one, so we recommend NTEP models and can check yours. TDA’s guidance (Legal for Trade Scales in the State of Texas) says a device with an NTEP certificate meets the Handbook 44 minimums. For counting that sets a price, choose an NTEP model such as the OHAUS Ranger Count 3000, and check any scale you already own with our free legal-for-trade scale checker. More background: what NTEP legal for trade means.
Calibration, service and rentals
Counts are only as good as the weight behind them, so calibrate at least once a year (how often to calibrate). Add calibration with a certificate to any scale above, by capacity, or see what scale calibration costs:
Up to 2.2 kg (FC-500Si, FC-500i, FC-2000i, RC31P1502):
In-house calibration + certificate ($95.00) NIST calibration + NIST-traceable certificate ($395.00)
Over 2.2 kg up to 6.2 kg (FC-5000i, GC-3K, HC-3Ki, B140-12, RC31P3):
In-house calibration + certificate ($195.00) NIST calibration + NIST-traceable certificate ($495.00)
Over 6.2 kg up to 35 kg (HC-15Ki, B140-30, RC31P15):
In-house calibration + certificate ($250.00) NIST calibration + NIST-traceable certificate ($595.00)
- On-site service: $295 + $2 per mile per visit in the Houston area, with calibration charged per scale. On-site calibration details.
- Mail-in calibration: ship your scale from anywhere, including counting scales bought elsewhere. How mail-in calibration works.
- Pickup in Cypress: order online and pick up at 21249 FM 529 Rd, Cypress, TX, by appointment.
- Repairs and rentals: we repair the brands we sell and rent all types of scales, including counting scales for a physical inventory.
Not sure which scale can count your part? Tell us the part, its weight per 100 pieces and your batch size. We will recommend a scale, set it up and calibrate it before it ships.
Small parts counting scale FAQ
What is the best scale for counting small parts?
Choose a counting scale whose minimum unit weight is far below your lightest part. For screws, washers and electronic components under about 1 g each, the A&D FC-500i (500 g x 0.05 g, minimum unit weight 0.0005 g in fine mode, $874.00) is our usual pick; for the tiniest parts, the FC-500Si goes down to 0.00005 g. For larger bins of hardware, the A&D HC-15Ki or Brecknell B140-30 cover 30 lb.
What is the minimum piece weight on a small parts counting scale?
It is the lightest single part the scale can count reliably. A&D lists two values: on the FC-500i it is 0.01 g in normal mode and 0.0005 g in fine mode, and on the FC-500Si 0.001 g and 0.00005 g. Brecknell lists 0.05 g for the B140-12 and 0.1 g for the B140-30. Keep your lightest part comfortably above the value for the mode you use.
How many pieces should I use as a sample for small parts?
Use more pieces when parts are light or vary in weight: 25, 50 or 100 instead of the default 10. Brecknell recommends a sample weight of at least 0.1% of capacity, for example 6 g on a 6 kg scale. A&D scales ask for a larger sample when the sample is too light, and ACAI refines the piece weight as you add more parts.
Why is my counting scale count off?
The usual causes are a sample that is too small, parts that vary in weight from lot to lot, a part lighter than the minimum unit weight, drafts or vibration, and a scale that needs calibration. Re-sample each new lot, use a bigger sample and count away from fans and doors. If the scale shows a code such as Lo or LACK, the sample is too light.
Can a counting scale count screws in a bin?
Yes. Place the empty bin on the scale and press tare, take the sample from the same parts, then pour in the rest. Choose a capacity that covers a full bin plus the bin itself, such as 30 lb (15 kg) for hardware bins.
Does a small parts counting scale need to be NTEP?
Counting stock for your own inventory does not set a price for a customer. If the count or weight is used to charge a customer, the scale is used for trade and must be legal for trade. TDA does not require an NTEP certificate for every device, but the scale must meet NIST Handbook 44 and suit its use; some scales do need one, so we recommend NTEP models and can check yours. The OHAUS Ranger Count 3000 models we sell are NTEP Class III.
Can MNM Scales calibrate a counting scale I bought somewhere else?
Yes. Mail-in calibration is open to scales bought anywhere, with an in-house or NIST-traceable certificate. In the Houston area, our technicians can also calibrate on site for a $295 visit plus $2 per mile, with calibration charged per scale.