How much should I tip a guide leading a free walking tour?

I usually tip what would be equivalent to US$ 5.00.

That's certainly up to you. I tip based on how good the tour/guide is. If the tour went where it advertised it would go and the guide was well informed and good at imparting what they know, I have tipped the approx amount I would have spent on a 'paid' tour - about $10/15 US. If the tour did not live up to it's hype or the guide was not well informed and did not show any interest in the area we were touring, I might cut that in half and give them $5. I have taken a 'free' tour that did not take us to all the places on it's stated itinerary, with a guide that was abysmally uninformed about the area we were touring (I knew more from my advance research than he did), and did not care at all that some of those on the tour were having trouble hearing him or keeping up with his fast pace. In that case I would (and did) walk away without tipping him anything. If a 'free' tour expects to make their money with tips they had better put out some effort to earn that tip.

Avoid those “free” tours. They are just a way to gain unfair competitive advantages over legitimate Tour guides. By making the Tour tip based, they don’t pay any taxes and don’t have to care for their guides, because they are not legitimate employees. The guides themselvees are usually just foreign Exchange students and the like, who dont have any knowledge of the local history or society other than what they have read in the script they are provided.
Just pay for a legitimate tour with a guides who actually knows their stuff and are paid a wage.

Very sensible advice Morton

It has been reported (I think by Rick himself) that the guides on the "free" tours pay the organization about 3 euros (or was it 3.50?) for each person who shows up for the tour. Therefore (sorry) I consider $5 seriously inadequate compensation if the guide is competent. My minimum is about 10 euros, and I'm not talking about high-cost cities like the capitals of western Europe.

I prefer tours with standard fees, as are often run by local tourist information offices, but I have used "free" tours when they offered specialized topics not otherwise available. I find the "free" tours to be a bit more about entertainment than the T.O. tours.

I haven't taken a free tour in either city, but I highly recommend paying for the Bike with Mike tour in Copenhagen http://bikecopenhagenwithmike.dk/ He's a riot, it's fun to see the city the way people who live there do (by bike!) and he provides all the bikes and helmets. One of the best things I did in Scandinavia.

I took a "free" walking tour in Copenhagen that was sponsored by the tourist office...I don't think they are trying to undercut the tour agencies. I usually tip the equivalent of about $10 for these tours, more if it was exceptionally good.

Look at the company's website to see how much a similar regular paid tour would cost. That's how much you should pay the free walking tour guide IF he meets your approval.

We love these tours, because the guide has to work hard to please and inform you. Otherwise he doesn't get paid!

Anita, of course they are trying to undercut the established Tour agencies. At least thats what the Tour agencies think, since they have taken the “free” tours to court.
Brooke if the guides are not qualified and don’t know anything about the places they are guiding you around other than their script, the threat of not getting paid won’t suddenly make them learn.

Brooke, do you often not pay people for services they have already given you??????

I've taken Free walking tours in many cities; and have never felt ripped off or that I was given wrong information.
I tip about E10; and in Amsterdam last year, tipped E20 as I thought the guide was really knowledgeable.
If you don't plan to tip at all afterward, then don't take a free tour, pay up front instead.

I fully support country neighbor Morten's view on free tours from a German perspective. I want to add the insight that cost of living in Denmark and especially Copenhagen is on a very high level in Europe, on the highest in EU (country index 141% compared to index 100 in average, Germany 105%; source). So, you will get much more for 5 EUR in Berlin than in Copenhagen (besides fact that currency is DKK). Therefore I like to vote for giving a little more than average tip in Copenhagen - of course only if you feel happy with the service you received.

We had an excellent Free Walking Tour in Copenhagen in 2014. Our guide was a graduate student at a University. We was well versed in local history, art and culture.

Further, we have taken several Free Waling Tours from Buenos Aires to Bath, etc. We have never been disappointed. Having taken many paid tours, we have not noticed a huge difference in the tour guide quality.

As for tipping, for a two or three hour "Free" tour, I usually give around $10-15 pp.

I agree with CL. We took one of the Bike with Mike tours in Munich, and we loved it! It was our second time to Munich (after a RS tour), and we saw different places, learned more history and really enjoyed the easy ride seeing so much of the city. Since that tour I have taken city bike tours in several locations - always a highlight!