What does a burn-up chart show about scope change that a burn-down chart hides?
answer
- One line against two lines
- Added work cancels completed work
- The moving target needs its own line
- A flat remaining line is ambiguous
basics
~20 sA burn-down plots one series, work remaining, so newly added work and completed work cancel out and the line barely moves. A burn-up plots two series, completed work and total scope, so a rising scope line makes growth visible.
solid answer
~50 sThe difference is structural: a **burn-down** has one line and a **burn-up** has two. A burn-down plots work remaining against time, so two independent facts — work finished and work added — enter the same number with opposite signs and cancel. A flat burn-down is therefore ambiguous: it can mean nobody delivered anything, or that the team delivered steadily while an equal amount of new work arrived. A burn-up separates them, plotting cumulative completed work against a total-scope line of its own, so growth appears as a step upward in the target rather than as an absence of progress. That makes the burn-up the honest chart wherever scope is expected to move — a release, or a goal spanning several windows — while a burn-down remains a cheap daily signal inside a short window whose scope is meant to be fixed.
code
pseudocode · 9 linesday completed discovered remaining total_scope
0 0 0 47 47
2 6 0 41 47
4 12 9 44 56
6 19 8 45 64
8 27 0 37 64
burn-down draws: remaining
burn-up draws: completed and total_scopego deeper
Recall which lines each chart carries: remaining work for a burn-down, completed work plus total scope for a burn-up. Being able to say what the axes are, and that the ideal line is only a reference, is enough at this level.
Explain the cancellation mechanically: completed work and discovered work meet in one number on a burn-down, so growth is invisible. Walk through a small worked example showing a flat line during a productive stretch.
Show judgement about which chart suits which window, and about audience: a burn-up makes scope growth a shared fact instead of an apparent failure by the team. Be ready to say when you stopped using a chart entirely.
Own the reporting tradeoff. A burn-up invites a conversation about who keeps adding scope, which is organisationally harder than a falling line but far more useful; be able to argue for the harder chart and to say what you will not use it for.
## Two charts, one structural difference A **burn-down chart** plots a single series: work remaining, against time. The vertical axis is whatever unit the team counts remaining work in — item counts, estimate units, hours — and the line is meant to fall toward zero at the window's end. Most burn-downs also carry a straight *ideal* line drawn from the starting amount to zero, purely as a reference. A **burn-up chart** plots two series against the same time axis: cumulative work completed, rising from zero, and the total amount of work in scope, drawn as a line of its own. Progress is the gap between the two lines, and the target is explicitly allowed to move. That one-line-versus-two-lines difference is the entire answer. | | Burn-down | Burn-up | | --- | --- | --- | | Series plotted | one: work remaining | two: completed, and total scope | | Work added mid-window | invisible; it cancels against completed work | visible; the scope line steps up | | Question it answers best | "will what is left fit in the time left?" | "how much is finished, and is the target moving?" | | Characteristic failure | a flat line is ambiguous | two lines take longer to read and explain | | Natural window | one short window with fixed scope | a release or a multi-window goal | ## Why a burn-down hides growth Because remaining work is a single number, work finished and work discovered enter it with opposite signs and cancel. Consider a window that opens with 47 units of work remaining. By day 4 the team has finished 12 units and 9 units of previously unknown work have been discovered, so the remaining figure reads 44. By day 6, 19 units are finished and 8 more have been discovered, so remaining reads 45 — higher than two days earlier. Read as a burn-down, the line drifted from 47 to 45 over six days: a team that appears to have achieved nothing and then recovered. Read as a burn-up, cumulative completed climbed 0, 6, 12, 19, 27 in a nearly straight line while total scope stepped 47, 56, 64. The team never slowed down for a moment; the finish line moved away from it. The same facts, and one of the two charts is structurally incapable of expressing them. What a burn-up lets you read that a burn-down cannot: - whether the target moved at all, in which direction, and by how much - whether a flat stretch was idleness or absorbed growth - whether the completion rate is steady even while the target recedes - where the two lines would meet if both continued — a forecast you can point at rather than assert - whether an improved outlook came from going faster or from removing scope ## When each chart is the right one - **Inside a short window whose scope is meant to be fixed**, a burn-down is a cheap daily signal, and the ambiguity is arguably the point: a flat line is there to provoke someone into asking "what got added?" on the day it happens. - **Across a release or a goal spanning several windows, where scope legitimately changes**, a burn-down verges on dishonest and a burn-up is the honest chart. - **When the audience includes people outside the team**, the burn-up is safer for a social reason as much as a technical one: it renders scope growth as a shared fact about the work rather than as an apparent absence of progress by the team. - **Neither chart compares one team with another.** The vertical unit is local to the team that defined it, so a cross-team comparison of the lines compares nothing. ## Reading either chart without fooling yourself 1. **The ideal line is a reference, not a commitment.** A team that tracks it exactly is a warning sign, not an achievement. 2. **A single point tells you nothing.** The signal is the slope over several days, and the interesting moment is a change of slope. 3. **Ask what the vertical unit is before drawing any conclusion.** Item counts and estimate units behave differently when the sizes of items are uneven. 4. **Discovered work has to be added in the window it was discovered.** Otherwise both charts lie, and the burn-up lies more quietly, because its scope line simply looks stable. 5. **The update discipline is the chart.** A chart brought up to date once, on the last day, is a drawing of a memory. ## What an interviewer is listening for The minimum is knowing which chart has which lines. What separates a solid answer is naming the cancellation — that work finished and work added meet in one number in a burn-down — and then saying what each chart is *for*, rather than which one is better. The best answers add that the charts describe the work and not the team, and that a chart nobody acts on the same day has stopped being useful whichever shape it has.
- A burn-down line has been flat for four days. What are the two very different explanations?Either nothing was finished, or work was finished at roughly the rate new work arrived. The chart cannot distinguish them, which is why the flat line is a prompt to ask rather than a conclusion. To tell them apart you need the two numbers separately: how much was completed in those four days and how much was added. Once you are tracking both, you have a burn-up in all but name.
- How would you make a burn-down honest about scope change without switching chart types?Annotate it: mark the days scope was added and by how much, or draw a second series showing cumulative additions beneath the remaining line. Either restores the fact the single line destroys. It is worth being clear that this is the burn-up's information arriving by another route — at which point the argument for keeping the burn-down is familiarity, not accuracy.
A burn-down is a fuel gauge. A burn-up is a fuel gauge next to a map that shows the destination moving.
saying these in an interview costs you the question
- Claims a burn-down chart makes newly added scope visible
- Reads a flat remaining line as a team that did nothing
- Treats the ideal reference line as a target to hit
- Says burn-up and burn-down differ only in direction
- Uses either chart to compare one team against another