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Tire Size Calculator

Built by Kevin Glover · @gloverbuilds · Verified formula

Compare tire sizes. Calculate diameter, circumference, and speedometer difference. Free tire calculator.

📅 Updated April 2026 ✅ Formula verified 📖 4 min read 🆓 Free · No sign-up

In this article

How to Use This Calculator
Tips for Best Results

3%-Regel

Gesamtdurchmesser ±3% vom Original. Groessere Reifen: Tacho zeigt weniger als real. TUeV-relevant! Im Fahrzeugschein: alle erlaubten Groessen.

Plus-Sizing

Groessere Felge + flacherer Reifen. 195/65R15 → 225/45R17: ~1% Durchmesseraenderung (ok).

⚡ CalcWolf Insight

Consumer Reports found that at 4/32 inch tread remaining (halfway worn), wet braking distance increases 30%. At 2/32 inch (legal minimum), stopping distance nearly doubles vs new tires.

Frequently asked questions

Kann ich wechseln?▾

Innerhalb ±3% Durchmesser. Darueber: Eintragung und TUeV.

Wann Reifen wechseln?▾

1,6 mm gesetzlich. 3 mm empfohlen fuer Sicherheit bei Naesse.

✓ Math logic verified against primary sources → See our verification process

Kevin Glover · @gloverbuilds

Founder, CalcWolf · GLVTS · Blickr

All formulas sourced from primary references — IRS publications, peer-reviewed research, and official standards. Results are tested against independent reference calculators before publishing. Rates and brackets updated when official sources change. Editorial policy →