Use this conversion chart as an approximate guide to Snellen vs Diopters in your eyesight improvement journey. If your prescription is higher than about -4.00 you will likely not find the Snellen chart very useful and should consider relying on Blur Distance in centimeters for measuring your progress.
Related: Guide to Measuring Myopia
| Snellen Chart | Diopter | Blur Distance |
| 20/500 | -5.00 | 20cm |
| 20/400 | -4.00 | 25cm |
| 20/300 | -3.50 | 28cm |
| 20/250 | -3.00 | 30cm |
| 20/200 (Line 1) | -2.50 | 40cm |
| 20/150 | -2.00 | 50cm |
| 20/100 (Line 2) | -1.50 | 67cm |
| 20/70 (Line 3) | -1.25 | 80cm |
| 20/50 (Line 4) | -1.00 | 100cm |
| 20/40 (Line 5) | -0.75 | 134cm |
| 20/30 (Line 6) | -0.50 | 200cm |
| 20/25 (Line 7) | -0.25 | 400cm |
| 20/20 (Line 8) | 0.00 | 600cm |
| 20/15 (Line 9) | N/A | 800cm |
| 20/13 (Line 10) | N/A | 1000cm |
| 20/10 (Line 11) | N/A | 1200cm |
