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NASA Task Load Index

NASA-TLX
psychologystemhealth sciencesPublic domain

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.

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 counter-intuitive — 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., 139-183.

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., 139-183. 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.