In a hurry?
You don't have to read the detailed explanation below! Simply use the automatic calculator below to convert your prescription instantly.
👓 Contact Lens Power Converter
Most prescriptions are for eyeglasses. Enter your data below to calculate the best contact lens prescription.
📋 Recommended Specifications
💡 Buying Tips:
- If your exact power isn't available, choose the lower value closest to yours (within 0.50).
- If you are a first-time wearer, please consult an optometrist.
⚠️ Disclaimer:
Calculations are based on optical formulas. When astigmatism is between -0.50 and -1.00, both "Spherical Equivalent" and "Toric" options are shown for reference. Comfort may vary based on lens material and base curve.
Calculations are based on optical formulas. When astigmatism is between -0.50 and -1.00, both "Spherical Equivalent" and "Toric" options are shown for reference. Comfort may vary based on lens material and base curve.
OR
Converting Glasses Prescriptions to Contact Lenses (Nearsighted)
👓➡️👁️ The Ultimate Cheat Sheet: Converting Your Glasses Rx to Contacts
Ready to level up your look with EyeCala lenses but confused by the numbers? We got you. If you have a prescription for glasses, you can't always use the exact same numbers for contacts. But don't stress—the math is simple. Let’s decode it. ✨
1️⃣ Know Your Stats (The Basics) 📖
Grab your glasses prescription. It usually looks something like this:
| OD (Right Eye) | OS (Left Eye) |
|---|---|
| -2.50 | -2.75 |
- ✅ OD = Right Eye 👉👁️
- ✅ OS = Left Eye 👈👁️
- ✅ Negative (-) = You're Nearsighted (Myopia). This guide is for you!
2️⃣ The Physics Check (Vertex Conversion) 🔄
Here's the tea: Glasses sit off your face, while contacts sit directly on your eye. That distance changes the power you need.
- 🎉 Under -4.00? You're good! Use the same number as your glasses.
- 🔽 -4.00 or Stronger? You need to "power down" slightly (make the number lower).
| Glasses Rx | Contacts Rx |
|---|---|
| -3.00 | -3.00 (Same) ✅ |
| -4.50 | -4.25 (Lower) 🔽 |
| -6.00 | -5.50 (Lower) 🔽 |
3️⃣ The Conversion Chart 📊
Don't want to do the math? Use our cheat sheet below to find your perfect EyeCala match:
Contact Lens Power (SPH) Chart
-4.00 to -5.25
Subtract 0.25
Glasses Contacts
-4.00
-3.75
-4.25
-4.00
-4.50
-4.25
-4.75
-4.50
-5.00
-4.75
-5.25
-5.00
-5.50 to -7.00
Subtract 0.50
Glasses Contacts
-5.50
-5.00
-5.75
-5.25
-6.00
-5.50
-6.25
-5.75
-6.50
-6.00
-6.75
-6.25
-7.00
-6.50
-7.25 to -8.50
Subtract 0.75
Glasses Contacts
-7.25
-6.50
-7.50
-6.75
-7.75
-7.00
-8.00
-7.25
-8.25
-7.50
-8.50
-7.75
-8.75 to -10.00
Subtract 1.00
Glasses Contacts
-8.75
-7.75
-9.00
-8.00
-9.25
-8.25
-9.50
-8.50
-9.75
-8.75
-10.00
-9.00
Is your prescription stronger than -10.00? Please visit an eye doctor. At that level, you need a professional fitting to ensure your vision is crisp and safe.
🔖 Pro Tip: Can't find your exact number in the dropdown menu? Always choose the closest lower number. It's easier for your eyes to adjust to slightly less power than too much.
4️⃣ Got Astigmatism? (CYL & AXIS) 🔍
If your prescription has numbers under "CYL" or "AXIS," you have astigmatism.
- Mild Astigmatism (CYL -1.00 or less): You can usually wear regular colored lenses! Check out the Spherical Equivalent (SE) math here.
- Higher Astigmatism? You need Toric lenses. Read our Toric Guide here to get the right fit.
5️⃣ Consult the Pros 🩺
We love a DIY moment, but not with your eye health. Always confirm your prescription with an eye care professional, especially if you're new to contacts. They ensure your lenses fit comfortably so you can wear them all day.
📌 TL;DR Checklist:
- ✅ Under -4.00: Use the same number.
- ✅ Over -4.00: Use the chart above (go lower).
- ✅ Mild Astigmatism: Use the SE conversion method.
- ✅ Strong Astigmatism: Stick to Toric lenses.
🌈✨ Ready to Transform? 💖
Now that you've got the numbers down, the fun part begins. Browse our collection and find the aesthetic that speaks to you. If you get stuck, email our besties at hello@eyecala.com!