Professional Tire & Wheel Fitment Calculator
Compare tire sizes with OEM-aware rolling diameter math — speedometer deviation, sidewall height, wheel offset and clearance, in one accurate side-by-side.
Built for enthusiasts, mechanics and wheel shoppers checking OEM replacement and plus-sizing.
- OEM-safe math
- Rolling diameter
- Offset & clearance
- Flush fitment
- Daily safe
- 2,000+ comparisons
- 141
- tire sizes
- 2,000+
- comparisons
- 5
- calculators
- Live
- fitment math
Current Tire
New Tire
Fitment · Scaled comparison
● Excellent fit
Diameter
+2.4 mm
+0.38%
Sidewall
-11.5 mm
Speedometer
100.4 km/h
at true 100
Clearance
Excellent fit
Ground line · Scaled comparison
Excellent Fit
Within ±3% — safe for daily driving
Diameter change
+2.4 mm
0.38%
Speedometer at 100
100.4 km/h
+0.38% error
Ground clearance
+1.2 mm
ride height delta
Sidewall change
-11.5 mm
revs/km: 501.8
Permalink for this comparison:
/compare/205-55-r16-vs-225-45-r17Why TireFitCalc
Built for accurate tire fitment
Deterministic sizing math grounded in real tire geometry — not estimates or marketing claims.
OEM-aware diameter math
Rolling diameter, sidewall height and rolling circumference computed from real ETRTO geometry.
True speedometer deviation
Indicated vs actual speed derived from the diameter ratio — not a fixed lookup table.
Offset & clearance analysis
Inner clearance, poke and track-width change from real wheel-width and ET inputs.
Wide fitment coverage
141 catalogued sizes, 2,000+ comparison pairs and OEM vehicle fitments in one place.
How the math works
Why you can trust these calculations
Every result on TireFitCalc is deterministic. Given the same inputs you'll always get the same output — no randomness, no model guesses, no scraped averages. The numbers come straight from tire geometry: width, aspect ratio, rim diameter, ET and wheel width.
Rolling diameter from real geometry
Diameter = rim + 2 × (width × aspect / 100), in millimetres — same formula tire manufacturers publish.
Speedometer deviation by ratio
Indicated vs actual speed is the diameter ratio between OEM and new size, expressed as %.
Offset & ET reasoning
Inner clearance, poke and track-width change derived from true wheel-width and ET, not approximations.
Realistic fitment tolerance
Recommendations stay inside ±3% diameter tolerance — the range most OEMs and tire shops consider safe.
Who it's for
Trusted by people who actually fit tires
From daily drivers to wrench-turners — the same math, different reasons to use it.
Enthusiasts
Plus-sizing, stance and clearance checks before buying wheels.
Mechanics
Quick speedometer-deviation and load-index checks at the bay.
Wheel & tire shoppers
Verify a new size before checkout — diameter, sidewall and fitment.
OEM replacement
Find safe substitute sizes within manufacturer tolerance.
Explore by task
What do you need to do?
Jump straight to the right tool for your fitment question.
Check speedometer error
Real vs indicated speed after a wheel/tire size change.
Tire pressure or load index
Adjusted PSI and load capacity per tire and axle.
Side-by-side
Popular tire size comparisons
Top-ranked plus-size and width-change matchups from our smart comparison engine.
Compare
245/45 R20 vs 275/40 R20
Δ 0.07% diameter
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245/45 R19 vs 275/40 R19
Δ 0.07% diameter
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215/60 R17 vs 235/55 R17
Δ 0.07% diameter
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245/35 R20 vs 285/30 R20
Δ 0.07% diameter
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245/45 R18 vs 275/40 R18
Δ 0.07% diameter
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235/45 R18 vs 265/40 R18
Δ 0.07% diameter
Compare
205/55 R16 vs 225/50 R16
Δ 0.08% diameter
Compare
215/40 R18 vs 245/35 R18
Δ 0.08% diameter
Compare
195/55 R16 vs 215/50 R16
Δ 0.08% diameter
Compare
255/50 R19 vs 255/55 R18
Δ 0.01% diameter
Compare
255/45 R20 vs 255/50 R19
Δ 0.01% diameter
Compare
255/40 R19 vs 255/45 R18
Δ 0.01% diameter
Tire database
Popular tire sizes
Quick links to top OEM and aftermarket fitments. Browse the full catalog or jump by rim diameter below.
145/70 R13
Specs →
155/70 R13
Specs →
155/80 R13
Specs →
165/70 R13
Specs →
175/70 R13
Specs →
165/65 R14
Specs →
165/70 R14
Specs →
175/65 R14
Specs →
175/70 R14
Specs →
185/60 R14
Specs →
185/65 R14
Specs →
185/70 R14
Specs →
195/60 R14
Specs →
175/65 R15
Specs →
185/55 R15
Specs →
185/60 R15
Specs →
185/65 R15
Specs →
195/50 R15
Specs →
195/55 R15
Specs →
195/60 R15
Specs →
195/65 R15
Specs →
205/60 R15
Specs →
205/65 R15
Specs →
205/70 R15
Specs →
OEM fitments
Popular vehicle fitments
Browse common OEM tire sizes and safe plus-size options for popular platforms.
BMW · E46
3 Series
1998–2006
OEM size
BMW · E90
3 Series
2005–2012
OEM size
BMW · F30
3 Series
2012–2019
OEM size
Mercedes-Benz · W203
C-Class
2000–2007
OEM size
Mercedes-Benz · W211
E-Class
2002–2009
OEM size
Mercedes-Benz · W212
E-Class
2009–2016
OEM size
More vehicles
- Audi A4 · B6205/55 R16
- Audi A4 · B8225/50 R17
- Audi A6 · C6225/55 R16
- Volkswagen Golf · Mk5195/65 R15
- Volkswagen Golf · Mk6195/65 R15
- Volkswagen Golf · Mk7205/55 R16
- Volkswagen Passat · B6215/55 R16
- Volkswagen Passat · B7215/55 R17
- Volkswagen Passat · B8215/55 R17
- Skoda Octavia · A5195/65 R15
- Skoda Octavia · A7205/55 R16
- Toyota Camry · XV40215/60 R16
- Toyota Camry · XV50215/55 R17
- Toyota Corolla · E150195/65 R15
- Toyota RAV4 · XA40225/65 R17
- Honda Civic · 8th Gen (FA/FD)205/55 R16
- Honda Accord · 8th Gen215/60 R16
- Ford Focus · Mk2195/65 R15
- Ford Focus · Mk3205/55 R16
- Opel Astra · H195/65 R15
- Opel Astra · J205/60 R16
- Renault Mégane · III205/55 R16
- Dacia Duster215/65 R16
- Hyundai Tucson225/60 R17
Knowledge base
Latest fitment guides
In-depth references on plus-sizing, offset, speedometer error and safe wheel upgrades.
Featured guide
How Speedometer Error Is Calculated
When you change tire size, your speedometer reading drifts. Here is exactly how the math works.
Read the full guide
Guide
Wheel Offset & Backspacing Explained
ET, offset, backspacing — the difference between a perfect fitment and rubbing.
Read article
Guide
What Tire Size Difference Is Acceptable?
The 3% rule that pros use when plus-sizing or downsizing tires.
Read article
Guide
Can Bigger Wheels Damage Your Suspension?
What plus-sizing does to ride quality, bearings, and bushings.
Read article
Guide
Tire Pressure Explained: PSI, Load and Tire Size Changes
What PSI really means, why the door placard matters more than any online calculator, and how a tire size change can shift the right pressure.
Read article
Most read by enthusiasts
- Tire Load Index Explained: How Much Weight Can a Tire Carry?
- Wheel Offset vs Backspacing: What Is the Difference?
- Plus-Sizing Guide: How to Upgrade Wheel Size Safely
- What Is Wheel Offset (ET)? A Complete Engineering Guide
- Backspacing vs Offset: Conversion, Formula and When to Use Each
- Flush vs Aggressive Fitment: Stance, Poke and the Real-World Limits
- How Wheel Offset Affects Handling, Scrub Radius and Bearing Life
- Wheel Spacer Guide: Stance, Safety and the Math Behind ET Shift
- Are Wheel Spacers Safe? Stud Engagement, Bearings and Real-World Limits
- Hub-Centric vs Universal Spacers: Why the Centering Interface Matters
- Spacer vs Lower-Offset Wheel: Which Is the Right Way to Get Flush?
By rim diameter
Browse tire sizes by wheel size
Jump to every catalogued size for a given rim — grouped for quick navigation.