Load, Pressure & Safety

Tire Load Index Comparator

Compare the load index of a replacement tire with the original. See the capacity gap per tire and per set in kg, lb and percent.

Load, Pressure & Safety

Compare replacement and original ratings.

Open Live Calculator

Tire Load Index Comparator: Tire Size Inputs

Compare two tire sizes here. Use the formulas and reference tables below for this tool's specific calculation.

ISO/TRA Compliant

Baseline Tire (T1)Stock OEM

Width (mm)

Aspect (%)

Rim (in)

Comparison Tire (T2)Proposed Setup

Width (mm)

Aspect (%)

Rim (in)

Baseline OD634.3 mm24.97"

Comparison OD637.2 mm25.09"

Diameter Variance+2.9 mm+0.46%

Speed @ 60 MPH60.3 MPH-4 revs/mi

How Tire Load Index Comparator Works?

The Tire Load Index Comparator works by decoding both load indexes into capacity and subtracting the original capacity from the replacement capacity. The tool uses 3 steps.

Enter the original index
Type the index from the placard or original tire, for example 98.
Enter the replacement index
Type the replacement index, for example 94.
Read the gap
The comparator returns −80 kg (−176 lb) per tire, −10.7%, and marks the replacement as below original.

Tire Load Index Comparator Formula

The Tire Load Index Comparator formula is ΔL = L(i_rep) − L(i_orig), and the pass rule is i_rep ≥ i_orig.

Capacity gapΔL = L(i_rep) − L(i_orig)

Percent gapΔL% = ΔL ÷ L(i_orig) × 100

Set gapΔL_set = 4 × ΔL

i_orig, i_rep: Original and replacement load index
L(i): Capacity from the load table (kg)

Worked example

Index 112 carries 1,120 kg (2,469 lb), and index 116 carries 1,250 kg (2,756 lb). The replacement adds 130 kg (287 lb) per tire, +11.6%, and 520 kg (1,146 lb) per set.

Tire Load Index Comparator Conversion Table

The Tire Load Index Comparator conversion table compares capacity for 7 original-to-replacement index changes.

Capacity gap for 7 index changes
Index change	Capacity	Gap per tire	Gap (%)	Result
91 → 94	615 → 670 kg	+55 kg (+121 lb)	+8.9%	Meets or exceeds
94 → 98	670 → 750 kg	+80 kg (+176 lb)	+11.9%	Meets or exceeds
98 → 102	750 → 850 kg	+100 kg (+220 lb)	+13.3%	Meets or exceeds
102 → 99	850 → 775 kg	-75 kg (-165 lb)	-8.8%	Below original
112 → 116	1120 → 1250 kg	+130 kg (+287 lb)	+11.6%	Meets or exceeds
121 → 123	1450 → 1550 kg	+100 kg (+220 lb)	+6.9%	Meets or exceeds
113 → 121	1150 → 1450 kg	+300 kg (+661 lb)	+26.1%	Meets or exceeds

What is Tire Load Index Comparator?

A Tire Load Index Comparator is a tool that compares the load rating of a replacement tire with the original tire. A replacement tire needs an equal or higher load index than the vehicle maker's specification.

Plus-size tires often carry a lower index than stock. A 225/40 R18 tire in standard load construction can carry 88 (560 kg) while a stock 225/45 R17 carries 91 (615 kg). Extra load (XL) versions restore the capacity.

Load index comparisons across construction types need care. A P-metric and an LT tire with the same index use different pressure references.

What are the uses of Tire Load Index Comparator?

There are 4 main uses of the Tire Load Index Comparator, including plus-size checks and SUV replacements.

Plus-size checks
Confirm a lower-profile tire keeps the stock rating.
SUV replacements
Avoid passenger tires with too little capacity for a heavy SUV.
Load upgrades
Measure the capacity gained from an LT or XL tire.
Inspection prep
Document compliance with the placard rating.