Looking to upgrade or swap your Mazda Miata tires and wheels? The Miata Tire Calculator helps you discover compatible tire sizes while preserving your car’s performance, safety, and speedometer accuracy.
Miata Tire Calculator
Compatible Tire Sizes
Based on your current tire size:
| Width (mm) | Aspect Ratio (%) | Wheel Size (in) | Overall Diameter (in) | Difference (%) |
|---|
Note: It’s generally recommended to stay within ±3% of your original tire diameter to avoid speedometer and handling issues.
🚘 What Is the Miata Tire Calculator?
The Miata Tire Calculator is a precision tool tailored specifically for all generations of the Mazda Miata (NA, NB, NC, ND). It computes:
- Current tire diameter based on width, aspect ratio, and wheel size
- Suggested compatible tire options when changing your wheel diameter
- Difference in diameter as a percentage, so you know if it’s within the safe ±3% margin
🔍 How the Calculator Works
1. Select Your Miata Model
Choose your generation:
- NA (1989–1997)
- NB (1999–2005)
- NC (2006–2015)
- ND (2016+)
Each model has different default tire width and ratio ranges.
2. Enter Your Current Tire Details
Input:
- Tire width in millimeters (e.g. 185)
- Aspect ratio (percentage of width)
- Current wheel diameter in inches
3. Enter Your New Wheel Size
Input the desired new wheel diameter to see which tires are still compatible.
4. Click “Calculate”
The tool displays:
- Your current tire diameter
- A table of recommended tire sizes for your new wheels
- Percentage difference from original size
- Highlighted best-fit options (±3% difference)
🧮 Behind the Scenes – Formula Explained
Tire Diameter (in inches) =
Wheel Diameter + 2 × ( (Width × Aspect Ratio) ÷ 100 ÷ 25.4 )
This formula accounts for both sidewalls and converts mm to inches.
Difference (%) =
(New Diameter – Original Diameter) ÷ Original Diameter × 100
Anything between –3% to +3% is considered acceptable for performance and speedometer calibration.
🔧 Example Scenario
Let’s say you have an NA Miata with:
- 185/60R14 tires
- Want to upgrade to 15-inch wheels
Here’s what the calculator does:
- Original diameter = ~22.74″
- Suggests 195/55R15 or 205/50R15 as close matches
- Shows % difference (e.g. +1.1%) to verify compatibility
📊 Key Features
✅ Supports All Miata Generations
✅ Compares current vs. new tire diameter
✅ Gives real-time top 10 compatible sizes
✅ Uses OEM-supported widths and ratios
✅ Clearly highlights safe vs. unsafe matches
✅ Responsive, clean interface
✅ No sign-up, no download required
📈 Result Table Preview
| Width | Aspect Ratio | Wheel | Diameter | Diff (%) |
|---|---|---|---|---|
| 195 | 55 | 15″ | 22.91″ | +0.75% |
| 205 | 50 | 15″ | 23.07″ | +1.45% |
| 215 | 45 | 15″ | 22.61″ | –0.57% |
| … | … | … | … | … |
Tires that fall within ±3% are styled with good-match classes for visibility.
⚠️ Why Staying Within 3% Matters
- 🚫 Speedometer Inaccuracy – Too much deviation skews your speed readout
- 🛞 Handling Issues – Oversized tires can rub or alter alignment
- 🔧 Fitment Problems – Larger tires may not fit inside wheel wells
- 📉 Fuel Efficiency Impact – Incorrect sizes can strain your drivetrain
❓ FAQs
1. Can I use this calculator for other cars?
It’s tailored for Miatas, but the math works universally.
2. What’s the best size for NA Miata on 15″ wheels?
Popular and safe choices: 195/50R15, 205/50R15
3. What is a good ±% range to stay within?
±3% is considered safe for most vehicles.
4. What happens if I exceed 3% difference?
It may affect your speedometer, handling, or suspension geometry.
5. Can I use this with different aspect ratios?
Yes! The tool explores multiple combinations automatically.
6. How many size options does it show?
It ranks the top 10 closest matches by diameter difference.
7. Does it factor wheel width too?
Not currently. It focuses on diameter only.
8. Are tire sizes model-specific?
Yes. The tool uses width/aspect values commonly used on each Miata generation.
9. Does it update results instantly?
Clicking “Calculate” triggers the instant result generation.
10. How accurate is the tool?
Very accurate—it uses real-world formulas and unit conversions.
11. Is this tool mobile-friendly?
Yes! It works on any screen size.
12. What if I enter invalid values?
You’ll see an alert to correct your input.
13. How is tire width measured?
In millimeters—section width from sidewall to sidewall.
14. Can I try multiple new wheel sizes?
Yes! Just enter a new diameter and recalculate.
15. Why is the aspect ratio important?
It directly affects the sidewall height and total diameter.
16. Are these results guaranteed to fit?
They are mathematically compatible—but always check physical clearance.
17. Is the tool free?
Yes. No cost, no sign-up.
18. Does it remember previous inputs?
No, but it’s quick to re-enter.
19. Can I export results?
Not yet. Use screenshot or copy/paste for now.
20. Will this work for lifted or modified Miatas?
It may give a baseline, but always check your mod’s specs and clearance.
🏁 Final Thoughts
Whether you’re upgrading to lightweight racing wheels or giving your Miata a fresh look, the Miata Tire Calculator ensures you choose tires that fit, perform, and protect. With accurate fitment data and smart matching, you’ll avoid costly mistakes and keep your ride smooth and stylish.