List of best responsive Tumblr themes, free and premium.
1Keep

Keep is a responsive grid Tumblr theme perfect for collecting all types of content, especially pictures.
2Pop Gallery

Pop Gallery is a Tumblr theme for visual portfolios, galleries, handcrafts shops, with the unique possibility to present distinct thumbnails for new, sold and reserved items. It has a beautiful and clean design with circular thumbnails.
3Sven

Sven is a portfolio theme made for artist/creators that want to showcase their works with a professional-looking design.
4Cherry

Cherry, a theme that is aesthetically beautiful with the addition of many customizable options available allowing you the capability of easily customizing the aesthetics of nearly every aspect of design including colors, images, hiding and disabling elements, social feeds and more.
5Stella

Stella is a classic blogging theme that is perfect for fashion bloggers. Packed with over 90 customization options, it is easy to give your blog a personal look.
6Hipster

Hipster is a free Tumblr theme with unique features like keyboard navigation and ability to display a beautiful large grid of your latest Instagram images in your posts.
7Tumblr Official

Tumblr Official is a default Tumblr theme, but it’s very customizable and its related posts feature is awesome! You can choose to display your posts in default (single-column) or grid layout.
8Focus Photography

Focus Photography is a very clean and minimal single-column Tumblr theme, perfect to showcase your photos.
9Spire

Spire is a single-column Tumblr theme that has a robust, clean and modern design that works for any type of blog.
10Shiyori

Shiyori is a responsive and multiple layout theme with many custom options to make your blog more interactive and lively.
14Copycat

Copycat is a theme with grid layout, you can choose the maximum number of columns shown (up to 5).
15Simple Webcomic

Simple Webcomic Theme is a responsive theme that has been design to make starting a webcomic quick, easy and free.