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NASA Task Load Index

NASA-TLX
psychologystemhealth sciencesPublic domain

Permission: Public domain. Free to use, reproduce and adapt without asking permission. Cite the original publication.

A multi-dimensional rating procedure that assesses perceived workload across six subscales. Widely used in human factors, aviation, healthcare, and HCI research. Two common versions are in use: the original weighted TLX (with pairwise comparisons) and the Raw TLX (unweighted mean of subscales).

Items
6
Response format
Continuous 0–100 scale (often presented as 21-point visual analog, 0 to 100 in increments of 5)
Version
1.0
Subscales
6

Ready-to-cite methods sentence

Perceived workload was measured with the NASA Task Load Index (NASA-TLX; Hart & Staveland, 1988). Participants rated six dimensions (Mental Demand, Physical Demand, Temporal Demand, Performance, Effort, and Frustration) on 0–100 continuous scales. An overall Raw TLX score was computed as the unweighted mean of the six subscale ratings.

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Reliability & validation

Notes
Internal-consistency alpha is not typically reported for NASA-TLX because the six subscales are intentionally multi-dimensional. Evidence for sensitivity and validity is reported across many task domains (see Hart, 2006, for a 20-year review).

Subscales

Mental DemandPhysical DemandTemporal DemandPerformanceEffortFrustration

Response anchors

Very Low · Very High

Known limitations

Placed in the public domain by NASA. Report whether Raw TLX or weighted TLX was used. The Performance anchor (0 = Perfect, 100 = Failure) is counterintuitive: a higher Performance rating means worse performance, and it should not be reverse-scored before averaging.

Original citation

Hart, S. G., & Staveland, L. E. (1988). Development of NASA-TLX (Task Load Index): Results of empirical and theoretical research. In P. A. Hancock & N. Meshkati (Eds.), Human Mental Workload (pp. 139-183). North-Holland.

https://doi.org/10.1016/S0166-4115(08)62386-9

Questions researchers ask

What does the NASA-TLX measure?

A multi-dimensional rating procedure that assesses perceived workload across six subscales. Widely used in human factors, aviation, healthcare, and HCI research. Two common versions are in use: the original weighted TLX (with pairwise comparisons) and the Raw TLX (unweighted mean of subscales).

How many items does the NASA-TLX have?

The NASA Task Load Index (NASA-TLX) has 6 items across 6 subscales: Mental Demand, Physical Demand, Temporal Demand, Performance, Effort, Frustration.

Is the NASA-TLX free to use?

The NASA-TLX is in the public domain: free to use, reproduce and adapt without seeking permission. Cite the original source.

Who developed the NASA-TLX, and how do I cite it?

Hart, S. G., & Staveland, L. E. (1988). Development of NASA-TLX (Task Load Index): Results of empirical and theoretical research. In P. A. Hancock & N. Meshkati (Eds.), Human Mental Workload (pp. 139-183). North-Holland. https://doi.org/10.1016/S0166-4115(08)62386-9

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Library entry verified January 2024. Metadata is provided for reference; item wording is available inside Folio Surveyor, subject to each instrument's licensing.