The total return index measures the overall market performance of the index, including capital appreciation and reinvested income from regular coupon or cash dividend payments. Any cash distributions are assumed to be reinvested back into the index on the coupon date / ex-dividend date of the distribution, and this contributes to the total return index performance.

Total return is calculated as the percentage value change plus net income accrual relative to the initial value of the asset, as recognised by the Global Investment Performance Standards  or GIPS®, a voluntary standards created and administered by the CFA Institute with the purpose of providing an industry-wide framework for comparing firms' investment performance. GIPS® is based on the fundamental principles of full disclosure and fair representation of investment performance results. 

TR_{t} = \sum\limits_{i}^{n} w_{i,t-1} (\frac{V_{i,t,RepCCY} + D_{i,t,RepCCY}}{V_{i,t-1,RepCCY}} - 1)

where:

TR_{t} denotes the total return of the index for the period between t-1 and t.
w_{i,t-1} represents an index-constituent weight (either value weighted, capped value weighted, or equally weighted) at time t-1.
V_{i,t,RepCCY} and V_{i,t-1,RepCCY} denote an index-constituent fair value expressed in the reporting currency at the end of quarter t and t-1 respectively.
D_{i,t,RepCCY} denotes an index-constituent coupon/dividend payment between quarter t and t-1 expressed in reporting currency.