Wheel Offset & Backspacing Calculator

Convert offset (mm) to backspacing (in) and back — plus hub-to-inner-edge distance and a rough fender vs frame clearance flag

Embed this calculator Free · no API key · keep the attribution link

Copy the snippet below to embed this calculator on your site. The attribution link must stay intact and dofollow (no rel="nofollow"). Browse all embeddable calculators

Theme Width

<div class="ttq-embed" style="max-width:100%;margin:0 auto;">
  <iframe src="https://testtalkhq.com/embed/wheel-offset-backspacing-calculator/?theme=light&utm_source=embed" width="100%" height="980" frameborder="0" loading="lazy" scrolling="no" title="Wheel Offset & Backspacing Calculator — TestTalkHQ" style="border:0;max-width:100%;width:100%;"></iframe>
  <p style="font:400 13px/1.4 system-ui,sans-serif;text-align:center;margin:6px 0 0;">Powered by the <a href="https://testtalkhq.com/wheel-offset-backspacing-calculator/?utm_source=embed&utm_medium=referral&utm_campaign=calculator_embed&utm_content=wheel-offset-backspacing-calculator" target="_blank" rel="noopener">Wheel Offset & Backspacing Calculator</a> from <a href="https://testtalkhq.com/?utm_source=embed&utm_medium=referral&utm_campaign=calculator_embed&utm_content=wheel-offset-backspacing-calculator" target="_blank" rel="noopener">TestTalkHQ</a></p>
</div>

<div class="ttq-embed" style="max-width:100%;margin:0 auto;">
  <iframe src="https://testtalkhq.com/embed/wheel-offset-backspacing-calculator/?theme=light&utm_source=embed" width="100%" height="980" frameborder="0" loading="lazy" scrolling="no" title="Wheel Offset & Backspacing Calculator — TestTalkHQ" style="border:0;max-width:100%;width:100%;"></iframe>
  <p style="font:400 13px/1.4 system-ui,sans-serif;text-align:center;margin:6px 0 0;">Powered by the <a href="https://testtalkhq.com/wheel-offset-backspacing-calculator/?utm_source=embed&utm_medium=referral&utm_campaign=calculator_embed&utm_content=wheel-offset-backspacing-calculator" target="_blank" rel="noopener">Wheel Offset & Backspacing Calculator</a> from <a href="https://testtalkhq.com/?utm_source=embed&utm_medium=referral&utm_campaign=calculator_embed&utm_content=wheel-offset-backspacing-calculator" target="_blank" rel="noopener">TestTalkHQ</a></p>
</div>
<script>(function(){function r(e){if(!e||!e.data||e.data.type!=="ttq-embed-height")return;var h=+e.data.height;if(!h)return;document.querySelectorAll("iframe[src*='testtalkhq.com/embed/']").forEach(function(f){if(!e.source||f.contentWindow===e.source)f.style.height=h+"px"})}window.addEventListener("message",r)})();</script>

Any trade

Contractor Job Estimator

$29.00

Buy

See all products

Checkout opens here — you stay on this page.

Wheel Fitment Shop Gear

The calculator converts ET and backspacing. A caliper confirms lip stack on a used wheel; a 1/2 in socket set and a click torque wrench install the wheel to spec after you mock-fit. None of this replaces a test-fit at lock and bump.

Starrett 0-6 inch electronic slide caliper

Starrett Stainless Steel Electronic Slide Caliper 0-6in EC799A

Measure lip thickness and hub-pad stack on a used wheel when the ET stamp is gone. Compare the tape backspace to the calculator before you order a replacement.

View on Amazon →

DEWALT Impact Socket Set Metric/SAE 1/2in Drive 23-Piece

Lug nuts and hub-centric rings come off and go back on during a mock-fit. Use impact sockets on an impact, then finish to spec with a torque wrench — not the gun.

View on Amazon →

CDI 2503MFRPH 1/2-Inch Drive Torque Wrench 30-250 ft-lb

After a spacer or a new-offset wheel, lug torque is not optional. Click to the vehicle spec in a star pattern on the ground, not hanging on a jack.

View on Amazon →

Check Rolling Diameter Too

A new wheel often arrives with a new tire size. Diameter percent, true vs indicated speed, and the common ±3% band.

Open Tire Size Calculator →

Tow Vehicle Wheel Setup

Custom wheels on a tow vehicle still need tongue-weight discipline. 10–15% band from loaded trailer weight.

Open Tongue Weight Calculator →

GCWR Headroom Before You Tow

Wheel offset does not raise hitch class. Leftover trailer budget after curb, passengers, and cargo.

Open Towing Capacity Calculator →

As an Amazon Associate, TestTalkHQ earns from qualifying purchases.

How to Use This Wheel Offset & Backspacing Calculator

Enter the listed (bead-seat) wheel width. Pick a bolt-pattern reference so the cheat sheet matches the wheel you are pricing. Choose offset mode if the catalog shows ET in millimeters, or backspacing mode if you taped an existing wheel. The results panel returns the other value, hub-to-inner-edge (same as backspacing), hub-to-outer-edge, and a rough clearance flag.

Backspacing (in) = (W + lip) / 2 + ET / 25.4
Offset (mm) = (BS − (W + lip) / 2) × 25.4

Worked 8 in / +35 mm example and how to tape a used wheel: guide. Fender rub vs strut/caliper rub: troubleshooting. Whether a spacer is the cheaper fix: comparison.

Wheel Offset & Backspacing Calculator