About

Inventory management in warehouses and construction sites often relies on weight-based counting rather than manual enumeration, which is labor-intensive and error-prone. This utility estimates the quantity of steel hardware (bolts, nuts, washers) by dividing the total net weight by the theoretical weight of a single unit. Precision is critical in logistics to prevent stock discrepancies and ensure accurate billing. Variations in manufacturing tolerances and steel density can introduce minor deviations; therefore, this tool calculates a probable count with a standard deviation warning.

The calculation accounts for the specific geometry of standard fasteners (ISO/DIN specs), including head volume and thread length. By subtracting tare weight (the container"s weight), the tool isolates the hardware mass for conversion. This method is standard practice in industrial supply chains for handling bulk items like M-series bolts and nuts.

Formulas

The core logic determines the count N by isolating the net mass of the hardware and dividing by the unit mass.

N ≈ W_total − W_tarew_unit

Where W_total is the gross weight, W_tare is the container weight, and w_unit is the weight of a single fastener derived from standard steel density (ρ ≈ 7.85 g/cm³).

Reference Data

Hardware Size	Type	Approx. Unit Weight (g)	Pcs per kg (Approx)
M6 x 20mm	Hex Bolt	6.20	161
M8 x 30mm	Hex Bolt	14.50	69
M10 x 50mm	Hex Bolt	38.40	26
M12 x 60mm	Hex Bolt	66.00	15
M6	Hex Nut	2.50	400
M8	Hex Nut	5.20	192
M10	Hex Nut	11.60	86
M12	Hex Nut	17.30	57
M6	Washer	1.10	909
M16 x 100mm	Hex Bolt	185.0	5

Frequently Asked Questions

Steel fasteners have a mass tolerance of roughly ±2% due to variations in head height, thread pitch, and plating thickness. For large quantities (e.g., 10,000 pieces), this deviation can result in a difference of 200 units. The tool provides an estimated range to account for this.

The database uses standard carbon steel density (7.85 g/cm³). Stainless steel (approx 8.00 g/cm³) is slightly heavier, meaning the actual count would be roughly 2% lower than calculated. Brass (8.40-8.73 g/cm³) would yield an even lower count for the same total weight.

Bulk hardware is rarely weighed loose. It is weighed in buckets, boxes, or on pallets. Neglecting the container"s weight (Tare) results in significant errors. For example, a 1 kg plastic bucket in a 10 kg total measurement introduces a 10% error if not subtracted.

The weights are approximated based on DIN 931/933 (Hexagon head bolts) and DIN 934 (Hexagon nuts) standards, assuming coarse threads and standard dimensions.