Calculated Ultraviolet Exposure Levels for a Healthy Vitamin D Status and no sunburn - description

UV-related web tools

Calculated Ultraviolet Exposure Levels for a Healthy Vitamin D Status and no sunburn - description

An acknowledged benefit of exposure to ultraviolet radiation is synthesis of vitamin D in human skin. Here we have defined a standard vitamin D dose based upon recommended requirements for vitamin D, and present a web-based tool that enables the user to calculate associated exposure times for any time and place. The recommended UV exposure times depends on latitude, time, total ozone, clouds, aerosols, surface reflectivity and altitude all of which can be specified by the user.

Author: Ola Engelsen

Copyright © 2011-2024 NILU

Last modified 2023.

The current model has undergone internal checking and validation. If you have any questions or comments on this service and how it could be improved for your needs, please contact the author. If you use this model for your work I would be interested to know about it.

If you use this program and publish the results, I would appreciate a lot if you cite it:
Webb, A.R. and O. Engelsen (2006) Calculated Ultraviolet Exposure Levels for a Healthy Vitamin D Status. Photochemistry and Photobiology. 82(6), 1697-1703.

Note! After the above manuscript was published, we have updated the vitamin D effective action spectrum to that of the CIE 174 report from 2006. The new SDDs for the Fitzpatrick skin types I-VI are 87.6, 109.4, 131.3, 197.0, 262.8, and 437.8 J m-2, respectively. These Standard Vitamin D doses (SDDs) are published in
Terushkin, V, A. Bender, E. L. Psaty, O. Engelsen, S. Q. Wang, A. C. Halpern (2010) Estimated equivalency of vitamin D production from natural sun exposure versus oral vitamin D supplementation across seasons at 2 U.S. latitudes, Journal of the American Academy of Dermatology. 62(6),929.e1-9.

We have now also downscaled the above SDDs by a factor of 1/1.32 as suggested in John C. Dowdy, Robert M. Sayre, Michael F. Holick, Holick's rule and vitamin D from sunlight, The Journal of Steroid Biochemistry and Molecular Biology, Volume 121, Issues 1-2, Proceedings of the 14th Vitamin D Workshop, July 2010, Pages 328-330, ISSN 0960-0760, DOI: 10.1016/j.jsbmb.2010.04.002. ( They obtained a more accurate fluorescent sunlamp emission spectrum for the underlying in vivo experiments.

The underlying simulations are done using the following model:
Engelsen O. and Kylling A., Fast simulation tool for ultraviolet radiation at the Earth's surface. Optical Engineering, 44 (4), 041012 (2005).

VitD_quartMEDandMED_v2 changelog

Method outline (see the journal article above for details)

FastRT was used to compute erythema and vitamin D effective UV doses. We then defined a Standard Vitamin D Dose (SDD) corresponding to the UV equivalent of an oral dose of 1000 IU vitamin D [Holick 2004c], i.e. the dose recommended to gain all the possible health benefits of vitamin D [Holick, 2004a]. Since radiation is incident on the skin, and the response to either irradiation or oral dosing is measured in the blood, the SDD must be qualified by the conditions of skin exposure. Following the formula of Holick [2004a] that recommends exposure to a quarter of a personal MED on a quarter of the skin area (hands, face and arms), we estimated the equivalent D effective UV. From this we calculated the time to acquire a quarter MED. Using the same solar exposure we then calculated the vitamin D effective dose acquired over the same time interval. This is then the SDD based on exposure of a quarter body surface area. A person exposing hands, face and arms (ca. 25% of the body) would now make sufficient vitamin D with 1 SDD, and will suffer a minimal erythema after 1 MED (2 SED), which by definition is 4 times the SDD exposure. Darker skinned people will require a larger UV dose to achieve the same effects.

The recommended blood serum level is under debate [Dawson-Hughes et al., 2005], but 30 ng(mL is widely recommended e.g., by [Hollis, 2005]. Clinical studies found 500-1,000 IU of vitamin D/day maintains blood serum levels of 30 ng/mL (75 nmol/L) [Tangpricha et al, 2003], [Heaney et al., 2003], [Meier et al., 2004]. We allow the user to change the recommended level. The user is also allowed to specify variable body exposure, because clothing changes with season.

In order to assess the fraction of the body that is exposed to the sun, the Lund and Browder Chart for skin burns provides an indication: Face 3.5%, neck 2%, trunk 26%, hands 6%, arms 14%, legs 14%, thighs 18%.


The resulting output, recommended UV exposure to obtain sufficient vitamin D, is two numbers in a single row at the bottom, i.e. hours:minutes.


CIE 174. Action spectrum for the production of previtamin D3 in human skin. CIE publication 174, Publisher: CIE, Vienna, Austria, 2006, ISBN 3 901 906 50 9.

Dawson-Hughes, B, R. P. Heaney, M. Holick, P. Lips, P. J. Meunier, R. Vieth (2005), Estimates of optimal vitamin D status, Osteoporos. Int., 16: 713-716.

Heaney R. P., K. M. Davies, T. C. Chen, et al. (2003) Human serum 25-hydroxycholecalciferol response to extended oral dosing with cholecalciferol. Am. J. Clin. Nutr. 77:204-210. Erratum in: Am. J. Clin. Nutr 2003;78:1047.

Holick, M. F. (2004a) The Vitamin D Advantage, iBooks.

Holick M. F. (2004c) Vitamin D: importance in the prevention of cancers, type 1 diabetes, heart disease and osteoporosis. Am. J. Clin. Nutr. 79: 362-7

Hollis B. W. (2005) Circulating 25-hydroxyvitamin D levels indicative of vitamin D sufficiency: implications for establishing a new effective dietary intake recommendation for vitamin D., J. Nutr. 135:317-322.

MacKinley, A. F. and B. L. Diffey, (Eds.)(1987) A reference action spectrum for ultraviolet induced erythema in human skin, CIE J., 6(1), 17-22.

MacLaughlin, J. A., R. R. Anderson and M. F. Holick (1982) Spectral character of sunlight modulates photosynthesis of previtamin D3 and its photoisomers in human skin. Science. 216, 1001-1003.

Meier C., H. W. Woitge, K. Witte, et al. (2004) Supplementation with oral vitamin D3 and calcium during winter prevents seasonal bone loss: a randomized controlled open-label prospective trial. J. Bone. Miner Res. 19:1221-1230.

Tangpricha V., P. Koutkia, S. M. Rieke, et al. (2003) Fortification of orange juice with vitamin D: novel approach for enhancing vitamin D nutritional health. Am. J. Clin. Nutr. 77:1478-1483.

Webb, A. R. , L. Kline and M. F. Holick (1988) Influence of season and latitude on the cutaneous synthesis of vitamin D3: exposure to winter sunlight in Boston and Edmonton will not promote vitamin D3 synthesis in human skin. J. Clin. Endocrinol. Metab. 67, 373-378.