ISO 20457 gives the general tolerances for plastic molded parts. Plastics shrink and warp, so molded parts need much wider tolerances than machined parts. The standard sorts them into tolerance groups TG1 to TG9, and a drawing names one group as the general tolerance, for example General tolerances ISO 20457 – TG6. Use the tables below for parts made by injection molding. All values are in millimetres.
ISO 20457 and DIN 16742: which standard is current?
| Standard | Status |
|---|---|
| DIN 16742 | German standard, edition 2013-10. Withdrawn. Its tolerance tables are still widely quoted on supplier drawings. |
| ISO 20457:2018 | First international edition, based on DIN 16742. Replaced by the 2026 edition. |
| ISO 20457:2026 | Second edition, published August 2026 (ISO/TC 61/SC 11). Current. Covers thermoplastics, thermoplastic elastomers and thermosets made by injection molding, injection compression molding, transfer molding, compression molding and rotational molding. |
| Values on this page | The DIN 16742:2013 tables for sizes 1 to 315 mm. Published ISO 20457 TG6 tables from suppliers match them. We have not compared them with the full ISO 20457:2026 text, so confirm with the current standard for contracts and critical features. |
Tolerance group basics
- Tolerance group (TG1 to TG9): sets how wide the tolerance is. Each step up makes it wider. TG1 is the tightest, TG9 the widest.
- W – tool-specific dimension: a dimension determined by the mold. It uses the tighter value in the table.
- NW – non-tool-specific dimension: a dimension not determined by the mold alone. It uses the wider value. In the standard, the NW value for one size range equals the W value of the next range up. The standard sets out how each feature is classified; ask us if you are unsure.
- Production series (1 to 4): series 1 is normal production and is the only series for general tolerances. Series 2 to 4 give tighter groups, and series 3 and 4 always need a separate agreement.
- Symmetrical limits: all values are plus and minus. ±0.31 mm on a 40 mm dimension means 39.69 to 40.31 mm.
Table 1 - W: tolerances for tool-specific dimensions (± mm)
| Nominal size (mm) | TG1 | TG2 | TG3 | TG4 | TG5 | TG6 | TG7 | TG8 | TG9 |
|---|---|---|---|---|---|---|---|---|---|
| 1 to 3 | ±0.007 | ±0.013 | ±0.020 | ±0.030 | ±0.05 | ±0.07 | ±0.13 | ±0.20 | ±0.30 |
| >3 to 6 | ±0.012 | ±0.020 | ±0.031 | ±0.05 | ±0.08 | ±0.12 | ±0.20 | ±0.31 | ±0.49 |
| >6 to 10 | ±0.018 | ±0.029 | ±0.05 | ±0.08 | ±0.11 | ±0.18 | ±0.29 | ±0.45 | ±0.75 |
| >10 to 18 | ±0.022 | ±0.035 | ±0.06 | ±0.09 | ±0.14 | ±0.22 | ±0.35 | ±0.55 | ±0.90 |
| >18 to 30 | ±0.026 | ±0.042 | ±0.07 | ±0.11 | ±0.17 | ±0.26 | ±0.42 | ±0.65 | ±1.05 |
| >30 to 50 | ±0.031 | ±0.05 | ±0.08 | ±0.13 | ±0.20 | ±0.31 | ±0.50 | ±0.80 | ±1.25 |
| >50 to 80 | ±0.037 | ±0.06 | ±0.10 | ±0.15 | ±0.23 | ±0.37 | ±0.60 | ±0.95 | ±1.50 |
| >80 to 120 | ±0.044 | ±0.09 | ±0.15 | ±0.23 | ±0.36 | ±0.57 | ±0.90 | ±1.40 | ±2.25 |
| >120 to 180 | n/a | ±0.13 | ±0.20 | ±0.32 | ±0.50 | ±0.80 | ±1.25 | ±2.00 | ±3.15 |
| >180 to 250 | n/a | ±0.15 | ±0.23 | ±0.35 | ±0.58 | ±0.93 | ±1.45 | ±2.30 | ±3.60 |
| >250 to 315 | n/a | ±0.16 | ±0.26 | ±0.41 | ±0.65 | ±1.05 | ±1.60 | ±2.60 | ±4.05 |
Table 2 - NW: tolerances for non-tool-specific dimensions (± mm)
| Nominal size (mm) | TG1 | TG2 | TG3 | TG4 | TG5 | TG6 | TG7 | TG8 | TG9 |
|---|---|---|---|---|---|---|---|---|---|
| 1 to 3 | ±0.012 | ±0.020 | ±0.031 | ±0.05 | ±0.08 | ±0.12 | ±0.20 | ±0.31 | ±0.30 |
| >3 to 6 | ±0.018 | ±0.029 | ±0.05 | ±0.08 | ±0.11 | ±0.18 | ±0.29 | ±0.45 | ±0.49 |
| >6 to 10 | ±0.022 | ±0.035 | ±0.06 | ±0.09 | ±0.14 | ±0.22 | ±0.35 | ±0.55 | ±0.75 |
| >10 to 18 | ±0.026 | ±0.042 | ±0.07 | ±0.11 | ±0.17 | ±0.26 | ±0.42 | ±0.65 | ±0.90 |
| >18 to 30 | ±0.031 | ±0.05 | ±0.08 | ±0.13 | ±0.20 | ±0.31 | ±0.50 | ±0.80 | ±1.05 |
| >30 to 50 | ±0.037 | ±0.06 | ±0.10 | ±0.15 | ±0.23 | ±0.37 | ±0.60 | ±0.95 | ±1.25 |
| >50 to 80 | ±0.044 | ±0.09 | ±0.15 | ±0.23 | ±0.36 | ±0.57 | ±0.90 | ±1.40 | ±1.50 |
| >80 to 120 | ±0.05 | ±0.13 | ±0.20 | ±0.32 | ±0.50 | ±0.80 | ±1.25 | ±2.00 | ±2.25 |
| >120 to 180 | n/a | ±0.15 | ±0.23 | ±0.35 | ±0.58 | ±0.93 | ±1.45 | ±2.30 | ±3.15 |
| >180 to 250 | n/a | ±0.16 | ±0.26 | ±0.41 | ±0.65 | ±1.05 | ±1.60 | ±2.60 | ±3.60 |
| >250 to 315 | n/a | ±0.18 | ±0.29 | ±0.45 | ±0.70 | ±1.15 | ±1.80 | ±2.85 | ±4.05 |
"n/a" = not defined by the standard (TG1 stops at 120 mm). TG9 has one value for both W and NW. Sizes below 1 mm and above 315 mm are not shown here; for them, see the standard or ask us.
Table 3 - Tolerance group by production series
| Production series | A | B | C | D | E | F |
|---|---|---|---|---|---|---|
| Series 1: Normal production | TG4 | TG5 | TG6 | TG7 | TG8 | TG9 |
| Series 2: Accurate production | TG3 | TG4 | TG5 | TG6 | TG7 | TG8 |
| Series 3: Precision production | TG2 | TG3 | TG4 | TG5 | TG6 | TG7 |
| Series 4: Precision special production | TG1 | TG2 | TG3 | TG4 | TG5 | TG6 |
Columns A to F are material and process groups assigned in the standard's annexes. Moving one series up (for example from 1 to 2) gives one group tighter, which needs better process control. Series 3 and 4 always need agreement between buyer and molder.
How to use the tables
Example 1 - 40 mm dimension, general tolerance TG6
| Tolerance | Limits | |
|---|---|---|
| W (tool-specific) | ±0.31 mm | 39.690 to 40.310 mm |
| NW (non-tool-specific) | ±0.37 mm | 39.630 to 40.370 mm |
Example 2 - 100 mm dimension, general tolerance TG5
| Tolerance | Limits | |
|---|---|---|
| W (tool-specific) | ±0.36 mm | 99.640 to 100.360 mm |
| NW (non-tool-specific) | ±0.50 mm | 99.500 to 100.500 mm |
How to show it on a drawing
Put the group in or next to the title block: General tolerances ISO 20457 – TG6 (older drawings: General tolerances DIN 16742 – TG6). If the part uses more than one material, the standard asks for the group to be set for each material. Give a direct tolerance only on the few dimensions that really need a tighter value, and review them early with the injection molding DFM checklist.
Tips
- Pick the group from what the part has to do. TG6 is a common general tolerance on supplier drawings, but critical features may need TG5 or better.
- Tight dimensions on molded parts cost more: more mold work, more process control and more inspection. See injection mold making and our quality control process.
- ISO 286 fits (H7, g6) are written for metal parts. For molded plastic features use the groups here, and keep ISO 286 and ISO 2768 for machined metal parts.
- Features that depend on the mold parting line, moving mold parts or a later operation can be harder to hold. Talk to the molder early about which dimensions are critical.
- Not covered here: sizes below 1 mm or above 315 mm, position tolerances, profile tolerances and the point system used to choose the group. Check the standard for these.
