[{"_id":"1","name":"name1"},{"_id":"2","name":"name2"},{"_id":"3","name":"name1"},{"_id":"4","name":"name3"},{"_id":"5","name":"name4"},{"_id":"6","name":"name3"},{"_id":"7","name":"name5"},{"_id":"8","name":"name5"},{"_id":"9","name":"name5"},{"_id":"10","name":"name6"},{"_id":"11","name":"thing6"},{"_id":"12","name":"table6"},{"_id":"13","name":"chair6"}]

db.collection.aggregate([{$sortByCount:"$name"},{$facet:{topItems:[{$limit:3}],otherItems:[{$skip:3},{$group:{_id:"Others",count:{$sum:"$count"}}}],totalitems:[{$group:{_id:null,total:{$sum:"$count"}}}]}},{$project:{allData:{$concatArrays:["$topItems","$otherItems"]},totalitems:{$arrayElemAt:["$totalitems.total",0]}}},{$unwind:"$allData"},{$project:{Item:"$allData._id",Count:"$allData.count",Percentage:{$round:[{$multiply:[100,{$divide:["$allData.count","$totalitems"]}]},0]}}}])