# Blog

### Excel Pivot Tables

Pivot tables are one of the most powerful and useful features in Excel. This article is an introduction to Pivot Tables and their benefits, and a step-by-step guide with sample data.

### Excel Formula Errors

Formula errors are useful, because they tell you clearly that something is wrong. This guide shows examples of each of the 9 formula errors you may run into, with an information on how to investigate and correct the error.

### How to lookup first and last match

If VLOOKUP finds more than one match, will you get the first match or the last match? It's a trick question. It depends :) This article explains this confusing topic in detail, with lots of examples.

### Excel formulas and functions

Formulas and functions are the bread and butter of Excel. They drive almost everything interesting and useful you will ever do in a spreadsheet. This article introduces the basic concepts you need to know to be proficient with formulas in Excel.

### The double negative in Excel formulas

The double negative coerces TRUE or FALSE values to their numeric equivalents, 1 and 0. This is a useful technique in many advanced formulas that work with cell ranges.

### 101 Excel Functions

Excel contains over 450 functions. Where should you start? This guide is a walkthrough of over 100 important functions in Excel. Click function names for details and linked examples.

### How to use formula criteria (50 examples)

Criteria are a key concept in Excel, but building useful criteria for text, numbers, dates, times, etc. is hard because it requires a good understanding of how Excel handles data. This guide will help you build formulas that work the first time with over 50 examples.

### Excel shows formula but not result

Every once in a while, you might find Excel behaving in a bizarre or unexpected way. One example is when you accidentally trigger the scroll lock feature. Another example is when one or more formulas suddenly stops working. Instead of a result, you see only a formula. What?

### Formula challenge - convert Y/N to days of week

In this challenge, the goal is to end up with a text string like "MWF" for Monday, Wednesday, Friday. The problem is that the weekdays are input like as yes/no abbreviations like "NYNYNYN" for "MWF". What formula will translate the "N" and "Y" to weekday abbreviations?

Every day, thousands of questions about Excel are posted on the internet. Many of these questions go unanswered because they are unclear. This article contains some tips on how to write a question that people will quickly understand and answer if they can.

### Formula challenge - multiple OR criteria

One problem that comes up a lot in Excel is counting or summing based on multiple OR conditions. For example, perhaps you need to analyze data and count orders in Seattle or Denver, for items that are Red, Blue, or Green? This can be surprisingly tricky, so naturally it makes a good challenge!

### Formula challenge - flag out of sequence codes

We have a simple list of 4-digit alphanumeric codes like A001, A002, A003, etc. What formula can we use to mark codes are "out of sequence" with previous entries? This problem includes two separate challenges.

### Formula challenge - 2D lookup and sum

In this formula challenge, we have data showing cups of coffee sold at a small kiosk for a week. What formula will look up and sum total cups sold after 12:00 PM on Tuesday and Thursday? Relevant cells are shaded in green.

### 29 ways to save time with Excel formulas

Working with formulas takes time, and too often a problem that seems simple ends up taking far too long. In this article, I share tips that will save you time when working with formulas in Excel.

### Formula challenge - build answer key for tests

In this formula challenge, we have four tests (Test A, Test B, Test C, and Test D), all with the same 19 questions, but listed in a different order. What formula can be used to match questions and construct an answer key for all tests? A perfect use for Excel's powerful lookup formulas.

### How to use INDEX and MATCH

This article explains in simple terms how to use INDEX and MATCH together to perform lookups. It takes a step-by-step approach, first explaining INDEX, then MATCH, then showing you how to combine the two functions together to create a dynamic two-way lookup.

### Excel custom number formats

Custom number formats control how numbers are look in Excel. The key benefit is that they change how a number looks without changing any data. They are a great way to save time in Excel because they perform a huge amount of formatting automatically. As a bonus, they make worksheets look more professional.

### Formula challenge - difference from last entry

The challenge - calculate the difference from the current and last entry, even when previous entries are skipped. This is one of those problems that seems simple at first glance, but is tricky when you look closely.

### How to make dependent dropdown lists in Excel

Once you start to add dropdown menus to your spreadsheets, you'll inevitably run into a challenge: how can you make one dropdown dynamically respond to another? More generally, how can you make the values in a dropdown list depend on another value in the worksheet?