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United Kingdom - variant flag dimensions

Design of the flag

See also:

1:2 flag

1:2 image by Clay Moss, 16 December 2006

The official specification is based on 1/30ths of the width (or height) of the flag. The St George's Cross is 6/30ths (1/5th) of the width, the fimbriations to it are 2/30ths (1/15th) of the width. The St Andrew's Cross is a total of 6/30ths (1/5th) of the width, measured perpendicularly to the diagonal. This is made up, in the top hoist corner, top to bottom, of 3/30ths white, 2/30ths red, 1/30th white. These dimensions apply regardless of the length of the flag. An accurate drawing of the flag can be found at this page, or on our page here.

My sources tell me that the proportions of Royal Navy flags were set at 1:2 for ensigns and jacks, and 2:3 for command flags " early in Queen Victoria's reign". Can anyone supply me with the actual date? The general consensus of opinion (backed by the measurements of the one surviving ensign I am aware of) seems to be that this was a confirmation of a situation which had been extant since the last quarter of the 18th Century?
Christopher Southworth, 18 April 2003

3:5 variant of the Union Jack


image by Graham Bartram	image by Martin Grieve, 6 April 2008

However, the army's version of the flag is not 1:2 but 3:5, so the two values of 25 along the bottom edge would be 20. In this case the diagonals of the St Patrick's cross are not quadrilaterals and are cut off as shown above. This is not a mistake - it is simply a result of the geometry. Both the 1:2 and 3:5 versions are official (although the government uses 1:2) and their specifications are given in BR20 Flags of All Nations, the British government's flag book.

There are other versions of the Union Flag: Queen's Colours are usually almost square and have very narrow fimbrations, with the red and white parts of the diagonal being of equal width; Queen's harbourmaster has a central Union Flag which is longer than 1:2; jacks for ships carrying blue ensigns are square and have a square Union Flag in the canton, etc.
Graham Bartram, 1 and 7 December 1999

The origin of the St. Patrick's cross introduced into the Union Jack in 1801 is a bit of a mystery. It appears that until the St. Patrick's cross was added to the Union Jack, there was no acknowledged St. Patrick's cross flag, certainly not one that was acknowledged in any form as a national flag for Ireland.
Mike Oettle, 15 December 2001

Note that a 3:5 British union jack is not just a regular 1:2 jack one squeezed to different ratio, as the vertical red and white “stripes” (cross arms) must keep the same width as the horizontal’s height.
António Martins-Tuválkin, 3 April 2008

2:3 variant of the Union Jack

images by Martin Grieve, 16 December 2023

The Union Jack is to be seen quite often at a ratio of 2:3, and of course appeared in this form on the 1928-1994 South African national flag. I received construction details from Christopher Southworth.
Martin Grieve, 16 December 2003

It seems that 2:3 were the proportions of the official Union Jacks flown in South Africa 1929 to 1957. In a letter to the First Lord of the Admiralty, dated 13 March 1929, Mr. A.A. Somerville wrote that he had it on good authority that the South African Government was ordering Union Jacks of 2:3 so that they would be of the same size and proportions as the Union Flag of South Africa, and asked if there were regulations concerning the proportions of the Union Jack. The reply was that, "it is believed at the Admiralty that there is no statutory authority beyond custom for the proportions in vogue for the Union Jack."
[National Archives (PRO) ADM 1/8968]
David Prothero, 7 April 2008

At the Paris 2024 Olympic Games, 2:3 ratio was officially prescribed for all national flags (except that of Nepal), including the Union Jack. The flag carried before the team at the opening ceremony (perhaps it is better to say "above", rather than "before", since they were on a boat, not walking around a stadium) conformed to this rule and so did the flags used at the prize award ceremonies. The small flags waved by the individual athletes during the opening ceremony did not conform, though, having been more oblong (about 1:2), as typically used in the UK; since their use was not considered official, there was clearly no obligation that they conform.
Tomislav Todorovic, 29 July 2025

Square variant of the Union Jack

image by António Martins

The square jack is rather mysterious topic, about which most sources that I have consulted are rather silent. If I understand rightly the Flaggenbuch, this square jack would in theory exist for any blue ensign approved.
Željko Heimer, 27 February 2002

As you wrote, theoretically there was a square jack for most Blue Ensigns, but in practice only a few were taken into use. Many departments operated only launches or small vessels that did not need a jack.

An Admiralty Memo in 1922 noted that the Red Jack was introduced in 1694 to prevent the use of the Union Jack. This was changed to a Blue Jack in 1864. Of 66 Royal Fleet Auxiliary Oilers and Petrol Carriers only two carried jacks. It would cost 110 pounds sterling to supply the rest with three jacks each, and cost an estimated 20 pounds per annum thereafter.

Admiralty Fleet Order 2189/22 of 1922 included the instruction that Royal Fleet Auxiliaries, Yard Craft and other vessels employed in the service of the Admiralty, and not commissioned as ships of war, were to fly the Blue Ensign defaced by the Admiralty badge (at that time a horizontal anchor), and on ceremonial occasions a jack defaced by the Admiralty badge. Two flags, one yard by one yard (91 cm x 91 cm), for use as jacks would be allowed each RFA attached to the Fleet Fuelling Service and Store Carrying Service. No jacks would be issued to vessels not accompanying the fleet.

image by António Martins

In 1974 the badge for RFAs was changed to a vertical anchor and the Blue Ensign with a horizontal anchor became the Government Service Ensign.

The only other defaced square jacks that I know of were; Hong Kong Naval Volunteer Force, Hong Kong 1924 badge, Straits Settlements Naval Volunteer Force, Straits Settlements badge, Royal Malayan Navy, Singapore badge, Royal East African Navy, REAN badge, Nigerian Naval Force, Nigeria badge.
David Prothero, 12 May 2002

In my limited experience of such documents, an Admiralty Warrant granting the right to fly a defaced blue ensign also specifically mentioned an accompanying defaced blue jack, and this is repeated in those more recently issued by the Ministry of Defence. A typical example is Jersey where the Admiralty Warrant of 2 March 1907 states that (in addition to the ensign) '...the said vessel (in this case the steam tug 'Duke of Normandy') shall be permitted to wear a small blue flag with a Union described in the canton at the upper corner next to the staff, as a jack, with the badge of Jersey in the fly thereof'. This right is repeated in the MoD Warrants granted on 15 June 1967 and in August 1997. Such jacks are, properly speaking and by convention square, and as such carry a square Union in the canton. On the other hand, as far as I can find out the right to use them is rarely, if ever, exercised (at least nowadays).
Christopher Southworth, 14 January 2003

It is possible that the reference to a jack in the Admiralty Warrant for the Blue Ensign is peculiar to Jersey, and was included only because a jack was specifically requested in addition to the ensign. The warrant for Jersey was unusual in that it could not be issued under the provisions of the Order in Council 9 July 1864 which abolished Squadron Colours, since the States of Jersey were not a Public Department, nor under the Colonial Naval Defence Act of 1865, since Jersey was not a colony. It was therefore issued as a special case under Sec.73(i) of the Merchant Shipping Act 1894; "any other ship or boat for the time being allowed to wear any other national colour (other than the Red Ensign) in pursuance of a warrant from His Majesty or from the Admiralty."
David Prothero, 15 January 2003

Yes the three warrants I referred to previously were all for Jersey, and upon checking I find that I have only one other (I thought I had two more). This is a copy of the MoD Warrant granting the right to fly a defaced blue ensign to Guernsey. It is undated (but was sent with an accompanying letter of 3 July 2000) and also confers the right to fly a defaced blue jack.

Of course the Admiralty and subsequent MoD Warrants under discussion were issued by virtue of the various Merchant Shipping Acts (the current wording is, it would appear, almost identical to that of the original), as, I presume, were those of the fleet auxiliary (since it forms part of the Merchant Marine)? What we need to know, and what I await information from the MoD on (if it ever arrives), is whether the granting of a defaced blue jack is general for Warrants issued to Government authorities, or, if the two cases in my possession are unique? According to the Admiralty librarian, sight of any Admiralty Warrants would require a visit to the Public Record Office.

The appearance of such a jack in the Flaggenbuch - considering the lengths gone to in ensuring the accuracy of that publication - seems to confirm that the practice had (at least in 1939 if not now) some sort of official sanction?
Christopher Southworth, 17 January 2003

The situation is probably much as it was in 1947 when Sir Gerald Wollaston, Norry and Ulster King of Arms, wrote to the U.S. of S. at the War Office.

"Flags flown at sea under the direction of the Admiralty are of the relative proportions of 2x1. This excessive length compared with the depth is unsuitable for heraldic flags (eg. the Royal Standard) in which the charges have to be distorted to fill the space, or in which (when this is not possible) they leave large spaces on either side unfilled; both resulting in bad heraldic design. The heraldic banner is properly a square flag, but for a flag flying in the wind from a flag pole some increase in length over the depth is admittedly desirable. These facts have long been recognised by the heraldic authorities. When, in 1938, the Earl Marshal, who is the controlling authority over heraldry and flags flown on land (which are mainly heraldic), laid down the flag proper to be flown on churches in the Provinces of Canterbury and York, opportunity was taken to state that flags on land should be of the approximate dimensions of 5x3 instead of 2x1. This was actually promulgated by me, as then Garter King of Arms and principal heraldic officer under the Earl Marshal, with his approval in a letter to the press; but as it had at the time principally reference to church flags it may not have had the advertisment which brought it to the notice of all people. However that may be, such knowledge does in fact spread, and when the Home Office, in 1943, desired to establish flags for the National Fire Service and and the Civil Defence Service, they agreed that, following the ruling of 1938, they should be made of the dimensions of 5x3. So, more recently, your office has, through the Central Ordnance Depot, altered the dimensions of Army flags, and the Air Ministry has adopted the same dimensions. While therefore the difference in size from flags flown at sea may not yet be universally known and accepted, and while it is neither possible nor desirable, to compel universal acceptance, I think it may be said that the dimensions of 5x3 for flags flown on land are officially accepted, and from this, no doubt, general acceptance will in due course follow. Anything which would tend to ensure this would be to the good.

As to the last paragraph of the letter from the Commonwealth of Australia, I would say that the Blue Ensign is primarily a flag to be flown at sea, and that all such flags come under the jurisdiction of the Admiralty and should of course conform to Admiralty dimensions. So far as it (with varying charges) may be flown partly at sea and partly on land - if that be the case - it may be inconvenient to have two sizes. There is nothing compulsory about the Earl Marshal's ruling, which is intended as a guidance to those concerned."

David Prothero, 24 November 2005

It may be worth making clear that situation is no longer exactly the same as regards the Australian flag, as it has since then been explicitly defined as 1:2 in the Flags Act.
Jonathan Dixon, 26 November 2005