Since this is a week when many politicians will be making comments about honoring the service of veterans, I thought some of this might be interesting. It is research from several reliable sources just using Google and searching "presidents and military experience.” 

Military experience is not a requirement for the presidency, but it has been in the experience of the majority those who have risen to the post of Commander and Chief.

Of the 46, only 12 have not served in some military capacity which includes state or territorial militias, reservists, and active-duty military service. Three, presidents Washington, Grant and Eisenhower were generals that played major roles in leading the nation through the three most important military conflicts in our country's history. Several others also achieved rank of general, brigadier or major general. 

Those who never served in any official military capacity include John Adams, Martin Van Buren, John Quincy Adams, and Grover Cleavland of the 19th Century and Woodrow Wilson, Warren Harding, Calvin Coolidge, Herbert Hoover, Bill Clinton, Barack Obama, Donald Trump and Joe Biden since 1900.  

The service of presidents since 1900 include:

Wm Mckinley, Civil War combat veteran from 1861-65 enlisted as private and discharged as a major; 

Theodore Roosevelt, combat veteran, Spanish American War, the only President to be awarded the Medal of  Honor (posthumously in 2001);

Howard Taft, Connecticut Home Guard;

Franklin Roosevelt, Assistant Sec. to the Navy (some do not deem this military service). FDR attempted to join uniformed service but was denied due to his physical disability. However, he was Commander in Chief for most of WWII;

Harry Truman, WWI combat veteran served in the Army Reserve until 1953; he also was Commander in Chief the last months of WWII and made the decision to use the atomic bomb.

Dwight Eisenhower, combat veteran and officer in WWI, Supreme Allied Commander and General of the Army WWII. As peacetime president he warned the country of the size and influence of the "Military industrial complex;"

John Kennedy, WWII combat veteran, Lt. in US Navy awarded Purple Heart and Navy and Marine Corps Medal;

Lyndon Johnson, WWII US Naval Reserve Commander, combat zone Silver Star recipient. 

Richard Nixon, WWII US Navy Commander, received two combat zone Battle Stars;

Gerald Ford, WWII Lt. Commander combat veteran, 1942-45;

Jimmy Carter, Midshipman from US Naval Academy, Lt. 1946-53 US Navy Reserve, 1953-61;

Ronald Reagan, US Army Reserve USAF Captain 1937- 42, active 1942-45 stateside service;

George HW Bush, Naval Aviator 1942- 45, shot down in combat, recipient Distinguished Flying Cross;

George W. Bush, Texas Air Guard 1st Lt. Stateside service, 1968-73;

Of the presidents who did not serve some had immediate family members (three generations), siblings, and/or children) who did, thus giving them some personal family perspective into military service. They include:

Martin Van Buren, whose son was a West Point graduate and served in combat in the Seminole Conflict and the Mexican American War;

Bill Clinton's biological father Wm Blyth (who died when Clinton was 3) and stepfather Roger Clinton were WWII combat veterans;

Barack Obama's maternal grandfather (whom he lived with for eight years and referred to as "father") and two maternal uncles, were combat veterans in WWII;

Joe Biden's son was a Captain in the Army National Guard and saw combat action in Iraq.

Some other interesting asides about the remaining presidents who did not serve:

John Adams did not serve in uniform but is considered a Founding Father of the Revolution and faced death for treason had the revolution failed.

John Q. Adams has no direct military service connection.

Grover Cleavland has deep Presbyterian/Quaker clerical roots and no immediate family military service.  He elected to pay a substitute $150 to take his place when he was conscripted for the Civil War on the grounds that he was sole supporter of his mother and sisters. He did serve as a county sheriff and personally oversaw the executions of two convicted murderers.  

Woodrow Wilson had deep Presbyterian clerical antiwar roots and no immediate family served. However, he was Commander in Chief after leading America into WWI despite a campaign promise not to. He ended his presidency campaigning to get the senate to ratify joining the League of Nations as an effort to prevent future wars. His effort failed.

Warren Harding also had a Quaker antiwar lineage and no immediate family members served in the military.

Calvin Coolidge had no immediate family members in the military, however, a great grandfather was a military officer.

Herbert Hoover's parents both came from Quaker families with antiwar sentiments and no immediate family members in the service. He did serve in Belgium as a war relief administrator providing food relief for people uprooted by war. 

Donald Trump attended high school at New York Military Academy and was an officer but declined ROTC service upon graduation. He has no immediate family members who have served in the military. Interesting footnote: His grandfather Fredrick Trump migrated from Bavaria, Germany in 1885, where he was due for "age compulsory" military training, became an American citizen, then went to Canada 1898-1901 during the Spanish American War. He attempted to return to Bavaria but was prohibited when it was learned he had avoided his compulsory service.