Title	Year	theme-website
24 – Could this be correct?	2026	Pupils and teachers will take a critical look at numbers, graphs and statements. What do you see? Should you add or multiply? Does this photo belong in this situation? Is the data being used correctly? What is being claimed? This Big Maths Day makes a number of new core objectives concrete, core objectives that are related to “mathematics and the world” and “mathematical thinking and working methods”.
23 – Fair share	2025	1005 schools During “Fair Sharing” on 19 March 2025, all children will get to work thinking about and playing with numbers and distribution situations. Examples include: dividing blocks fairly among boxes in the playroom (groups 1-2), filling backpacks and colouring squares (groups 3-4), donkeys with table products (groups 5-6) and puzzles with postcodes (groups 7-8). Website
22 – Data in the picture	2024	970 schools Central to virtually all activities during this 22nd Big Maths Day, with the theme “Understanding Data”, is learning how to “use” data: reading, interpreting, collecting and compiling it. In fact, this theme is a nod to the new core objectives for arithmetic and mathematics that were recently presented to the minister. Participation in this Big Maths Day therefore also provides an indirect insight into one of the important core objectives. In short, the day was spent working with statistics, with a strong focus on underlying skills such as collecting, organising, categorising, reviewing and visualising. Website
21 – The Waste Parade	2023	1150 schools The pupils will tackle challenging arithmetic and mathematics assignments, this time focusing on the creation of waste and the reuse and reduction of waste. All kinds of arithmetic and mathematical skills will be covered. They will also use their creativity to make something beautiful out of waste. Website
20 – The Architect makes the construction	2022	986 schools The participating schools embark on an adventure and start building. And thinking about building. Combining brainpower with what you can do with your hands. The children can then imagine what it is like to be an architect or a structural engineer. Or simply a builder. Drawing, estimating, categorising, planning: building involves a lot of “mathematical activities”. Website
19 – On a mathematical journey	2021	724 schools The children set off on their journey from school and will be surprised at how much arithmetic you use when travelling. People who go on holiday are often unaware of all the “calculations” involved. Planning, being on time, knowing where to go, being able to calculate with a foreign currency, keeping track of your expenses, being able to read a timetable: arithmetic is present in all these activities and is made explicit and experienced together on this Big Arithmetic Day, in appealing contexts and supported by travel stories. Website
18 – The Number Factory	2020	1250 schools We only have 10 digits (0 to 9), but with them we can count beyond the number of atoms in the universe. On this Big Maths Day, pupils explore what numbers are and what you can do with them at their own level. Of course, it’s not just about numbers, but also the digits that make up the numbers, the relationship between numbers, the places where you encounter numbers in everyday life, special numbers with special properties, and how you can create numbers. Website
17 – Out of proportion	2019	1235 schools The title of the seventeenth Big Maths Day is “Out of proportion”. During Big Maths Day, children explore situations involving proportions. In many of the activities, the proportions are different from what you would expect. When tackling the problems, children work with proportions, but also with measurement and geometry. Website
16 – The school as a warehouse	2018	1499 schools The theme of this 16th edition is “The school as a warehouse”. The children will think systematically during activities such as: inventorying, stacking, moving, coding. Children will think systematically during activities such as: inventorying, stacking, moving, coding. Website
15 – Measuring, moving and constructing	2017	1279 schools During the Great Maths Day, children explore their own environment and other recognisable places, mainly through measurement and geometry activities. The assignments are divided into four levels (groups 1-2, groups 3-4, groups 5-6, groups 7-8). These levels are only an indication; teachers can decide for themselves what is appropriate for their own group. Website
14 – Let’s have a look behind the code	2016	1301 schools The codes discussed during this Big Maths Day 2016 are reminiscent of the codes used in computers. Here too, the codes describe a method or sequence, but without the involvement of computers. Website
13 – Mathematics (geometry) and art	2015	1275 schools This year’s Big Maths Day is all about the art of arithmetic. Patterns, symmetry, geometry, measurement – it’s all covered. Museum Boijmans Van Beuningen is a partner of Big Maths Day 2015. Website
12 – Classroom statistics	2014	1200 schools During the twelfth Big Maths Day, all groups will present their class. This means that the children will create various graphs about what characterises them and what concerns them. The activities during the Big Maths Day are part of the new domain of connections. Creating a graph involves collecting data. Once the data has been collected, it is important that the children carefully consider how to organise this data in order to create a clear picture. This picture helps to gain insight into how you can accurately portray your daily life. But that’s not all. It also helps you get to know yourself and your group. Website
11 – Amusement Park	2013	904 schools The idea behind “Playing with measurement and geometry” is that play at all levels requires exploring space. This happens, for example, when young children look for a good hiding place when playing hide and seek, when they wonder how to move to get very high on a swing, or when they need to give someone a push to get the best effect on the swing. Young children run around and play with balls. In both cases, questions about exploring space are obvious. In the games played by older pupils, questions about understanding space are also obvious. However, they are better than younger pupils at explaining what they encounter in their games. Think, for example, of figuring out why one roller coaster goes very fast and another does not. Pupils realise that this has to do with the difference in height and how steep the descent is. Website
10 – Animals and Math	2012	830 schools The theme for the tenth Big Maths Day is animals. This theme offers numerous opportunities for maths. In the reading guide section, this is elaborated in terms of learning pathways. There you can also read how this theme has been developed for groups 1 and 2, 3 and 4, 5 and 6, and for groups 7 and 8. Website
9 – Are you sure?	2011	869 schools Reasoning and combining. During the ninth Big Maths Day, pupils explore all kinds of situations in which we ask them to draw and count possibilities and where chance plays a role at the children’s level. Children wonder whether games or situations are fair or not. During the Big Maths Day, children investigate challenging situations that not only encourage experimentation. Pupils look for patterns in situations that are initially confusing. Website
8 – Body measurement	2010	985 schools Measuring with and on the body. Measuring with natural measures, designing and exploring measuring instruments, acquiring measurement references and graphically representing measurement results in order to then search for relationships between measures. Website
7 – Money	2009	732 schools This is the book for the seventh Great Maths Day. If you compare this book with those from previous years, you will see that we have again chosen to develop activities at four levels this year, and that we are again planning a school-wide start to the Great Maths Day. Two chapters in this book are new. After this foreword, you will find a reading guide. The “Reading Guide” on pages 9-12 offers you options for tailoring the Big Maths Day to your needs. In addition, after the chapters describing the activities for the groups, a chapter has been added that offers you ideas for continuing activities around this year’s chosen theme after the Big Maths Day. The chapter “Getting started with ‘Value for money”’ on pages 135-147 points you in the direction of many computer games, board games, magic tricks and exhibitions. It shows that the theme of the Big Maths Day lends itself to many more activities than can fit into half a day. Website
6 – It’s about time	2008	683 schools Children regularly encounter time in primary education. This happens in arithmetic and mathematics lessons, for example, when learning to tell the time. But telling the time is certainly not the only time the subject of “time” is discussed. It also happens when children experience that some things take a long time and others only a short time, even though they involve the same amount of time. Children also work with time when they use or design timekeeping instruments. In addition, children in the upper grades learn that there are time differences on Earth and how these can be explained. The sixth Big Maths Day shows that much of this “time” that is discussed in primary school is also the “time” of arithmetic and mathematics, and that considering “time” from an arithmetic and mathematical perspective helps children to learn more about what “time” has to offer. Website
5 – Geometry, patterns and art	2007	673 schools During the Great Maths Day 2007, the focus was on creating and investigating patterns. Website
4 – Playing with numbers	2006	637 schools In the lower grades, the Big Maths Day takes place in the big number forest. This forest is home to special trees, numbers and other animals. The middle school project focused on a circuit with activities related to numbers. The pupils work in small groups on various assignments related to numbers, such as finding out what forms numbers can take, searching for special numbers, and estimating quantities. In the upper school, we focus on special number sequences in nature. The famous Fibonacci sequence is central to this. The children first conduct their own research, for example by measuring their own bodies. In this way, they discover regularity in proportions. Website
3 – Counting, tally, drawing. Collect, order and visualize	2005	398 schools We pay close attention to numbers and quantities (counting), organising and categorising (tallying) and presenting data (drawing). The children have been actively engaged with the story of Mr Spaarman (groups 1, 2 and 3), conducting experiments and collecting data (groups 4, 5 and 6) and developing their own research questions (groups 7 and 8). Website
2 – Geometry and measurement	2004	509 schools Activities based on larger thematic assignments centred around an island. Website
1 – Piloting the idea …	2003	20 schools This was a first pilot, coming from the RekenNet project, and a first idea from Leen Streefland, Freudenthal Institute. Website

The Freudenthal Institute started the Big Mathematics Day (BMD; in dutch ‘Grote Rekendag’) 25 years ago to let pupils and teachers experience that learning and teaching mathematics could be fun, could be interesting, and could also more profound. We did hope to show that a different way of teaching mathematics was possible, different from the way mathematics was taught in most classes.

Our reasons for developing a new BMD each year have not changed, and in fact the urgency has increased. This activity should focus on insight, on developing and using core mathematical ideas. This can be achieved through:

• Regularly have students solve open-ended problems;
• The teacher adopts a restrained approach, leaving the thinking to the students;
• Students work together, discussing their ideas;
• The teacher facilitates a discussion about underlying mathematical ideas.

But this is not what we observed in the schools 25 years ago, and we see it even less in the Dutch schools nowadays. After many years in which the Freudenthal approach (Realistic Mathematics Education, RME) was respected – but followed only superficially – we have new ‘political’ interference. In the public opinion, the performance of Dutch children in mathematics became perceived as declining. This was not substantiated by facts, but it resulted in an emphasis on traditional teaching. There is a general believe in ‘direct instruction’ as the best way to improve performance.
Thus what we see in schools nowadays is quite different from what ‘rich mathematics education’ should focus on. The current ’emphasis’ is on teaching procedures through demonstration and imitation. Insight is expected to develop through clear explanation by the teacher.
We must conclude that the ideas of RME do not resonate that much in mathematics teaching in the Netherlands. By organizing the BMD and other activities we hope to change the practice of teaching.

Research questions

The Big Mathematics Day (BMD) gives a strong opportunity to focus on cooperative research between the CN (the Chinese Universities involved) and NL (the Freudenthal Institute of Utrecht University). We perceive a gap between the ideals of RME and the daily practice in Dutch schools. This leads to questions like:

• Does the gap exist? What does RME say and what is the school practice?
• Is that gap experienced? Do teachers see the difference between a BMD activity and a method lesson? Do students see that difference?
• Would teachers and students like to have more education like the BMD?
• Does the BMD bring about changes in regular school lessons?

Cooperation with the Chinese counterparts could add to this:

• Is there a similar gap between ideals and practice in the Chinese schools (for example in the daily work of the ‘New Century Mathematics Textbooks’?
• Does organizing a Big Mathematics Day contribute to desired changes in teaching practices in the Chinese schools?

In the Freudenthal Institute we had insufficient resources to initiate this kind of research, although we published a lot in the more popular Dutch journals for (mathematics) education.
Cooperation with Chinese Universities is more than welcome: comparing the teaching practices in both countries and studying the effect of the BMD on teaching practice, could lead to a discussion about the actual practice of mathematics teaching in primary schools, and what RME has to offer to this practice.

• Jonker, V., Wijers, M., Abels, M. and Keijzer, R. (2016). Let’s have a look behind the code. The Big Mathematics Day 2016 (Netherlands) about coding without computer (PDF), PATT (pp. 8). De Bilt, the Netherlands: PATT.
• Van Galen, F. and Keijzer, R. (2016). Designing a Mathematics Day (PDF) Educational Designer, 3.
• Wijers, M. and Jonker, V. (2011). Change and counting: example from the Big Math Day 2010 (PDF). Utrecht: Utrecht University, Freudenthal Institute.

Dutch publications, see the dutch website on Grote Rekendag

• Dong, Y., Shao, Y., Zhou, D. and Liu, J. (2025). Experienced teachers’ beliefs about the conception of student creativity in primary mathematics (PDF) Educational Studies in Mathematics doi:10.1007/s10649-025-10474-1.
• Doorman, M., Bos, R., de Haan, D., Jonker, V., Mol, A. and Wijers, M. (2019). Making and Implementing a Mathematics Day Challenge as a Makerspace for Teams of Students (PDF) International Journal of Science and Mathematics Education, 17, 149––165 doi:10.1007/s10763-019-09995-y.
• Freudenthal, H. (1991). Revisiting mathematics education. China lectures (PDF). Dordrecht: Kluwer Academic Publishers.
• Huang, L., Doorman, L. M. and van Joolingen, W. R. (2020). Inquiry-Based Learning Practices in Lower-Secondary Mathematics Education Reported by Students from China and the Netherlands (PDF) International Journal of Science and Mathematics Education, 19(7) doi:10.1007/s10763-020-10122-5.
• Liu, Q., Liu, J., Zhang, J., Dong, Y. and Xie, Z. (2025). Researching the Development of China’s Mathematics Textbook for Primary Grades: A Participatory Action Research Study (PDF) ZDM – Mathematics Education, 57(5), 905–920 doi:10.1007/s11858-025-01682-3.
• Misailidou, C. and Keijzer, R. (2019). Making mathematics fun: the ‘fear room’ game (PDF), CERME 11.
• Wang, T., Tian, Y., Yang, J. and Liu, J. (2025). Opportunities to Learn Mathematical Modelling in NCM Primary Textbook: A Case Study of NCM Textbook for Grade 6 (PDF). In (pp. 24–30): Springer Nature Singapore.