Free tools

Scale math, stagger and gearing — done.

The same formulas the PITVUALT app uses, free in your browser. In the app they come prefilled from your car’s current setup. Nothing you type here leaves this page.

Corner weights

Enter each corner off the scales, in pounds, with the driver in.

Total
—
Left
—
Rear
—
Cross (wedge)
—
Bite (LR−RR)
—

Hit a number

  • —
  • —
  • —

Percentages rounded to 0.1. Check your class rules; the tech official decides.

Stagger

Taped circumference, in inches. Rear stagger = RR − LR.

Measurement type

Stagger

—

RPM at end of straight

RPM = mph × gear × trans × 336.13 ÷ tire diameter.

RPM

—

—

Check your class rules for a max gear ratio before you swap.

Density altitude & HP correction

Use station (absolute) pressure, not the sea-level number from the weather report.

Density altitude
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Air density
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HP vs SAE standard
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SAE J1349-style correction; the reference day is 77°F and 29.23 inHg dry, so cool standard-day air reads positive.

In the app

Save it with the setup. Check it before tech.

In PITVUALT these numbers save with every setup, light up orange when they change, and get checked against your class limits — offline, in the pits.

One email when the app drops at your track, with details of the founders offer (first 300 Pro annual subscribers after launch; joining the list doesn’t reserve it). We collect your email, plus class and home track if you give them. See our Privacy Policy. No spam, and we never sell your address. Accounts are for racers 18 and up; parents add young drivers inside their own account. Double-check your email — we use it exactly as typed.

Calculator FAQ

What’s cross weight (wedge)?
Cross is RF + LR divided by total weight. On an oval it’s usually called wedge. More cross generally tightens the car on corner exit; less frees it up. Every car is different — log what you change and how it felt.
What’s bite?
Bite here is LR minus RR in pounds. Positive bite means the left rear is carrying more than the right rear.
How do I measure stagger?
Tape the tire circumference at the same pressure and temperature on both sides, then subtract: RR − LR for rear stagger, RF − LF for front. If you only have diameters, switch to diameter mode and we’ll multiply by π.
Why does my RPM number differ from my tach?
The formula assumes no tire growth and no slip. Real tires grow at speed and the car is never exactly at the speed you typed. Use it to compare gears, not to predict a tach reading to the RPM.
Is station pressure the same as the weather report?
No. Weather reports give sea-level pressure. Density altitude needs station (absolute) pressure at the track. The app converts it for you using the track’s elevation.