Mold Tolerance Standards: ISO, DIN, and National Standards for Injection Molds
Last updated: June 19, 2026
Introduction to Mold Tolerances
Mold tolerances define allowable dimensional variation in mold components and the parts they produce. Understanding tolerance standards helps communicate precise quality requirements and manage cost expectations.
SPI Mold Classification
| Class | Description | Cycles | Tolerance (mm) |
|---|
| 101 | Premium production | 1,000,000+ | +/- 0.005-0.013 |
| 102 | Medium production | 500,000-1M | +/- 0.013-0.025 |
| 103 | Limited production | 100,000-500k | +/- 0.025-0.050 |
| 104 | Prototype/Low volume | <100,000 | +/- 0.050-0.100 |
ISO 2768 General Tolerances
| Class | 0.5-3mm | 3-6mm | 6-30mm | 30-120mm |
|---|
| f (fine) | +/-0.05 | +/-0.05 | +/-0.10 | +/-0.15 |
| m (medium) | +/-0.10 | +/-0.10 | +/-0.20 | +/-0.30 |
| c (coarse) | +/-0.15 | +/-0.20 | +/-0.50 | +/-0.80 |
| v (very coarse) | +/-0.30 | +/-0.50 | +/-1.00 | +/-1.50 |
DIN 16749 Precision Classes
- Class 1 (Fine): +/-0.01mm. For precision optics, medical.
- Class 2 (Medium): +/-0.02mm. For automotive, electronics.
- Class 3 (Coarse): +/-0.05mm. For packaging, non-critical.
Practical Component Tolerances
| Component | Typical Tolerance (mm) |
|---|
| Cavity width/length | +/- 0.010-0.025 |
| Core diameter | +/- 0.005-0.010 |
| Guide pin/bushing | +/- 0.005-0.010 |
| Ejector pin holes | +0.010 / +0.020 |
| Cooling channel position | +/- 0.5-1.0 |
Cost vs. Precision
Moving from Class 103 to 102 adds 30-50% cost. Moving from 102 to 101 adds another 40-70%. Always specify the loosest acceptable tolerance for each dimension.