Project Budget Burn Calculator

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Currency:

Total budget:

Actual spend to date:

Committed cost:

Project start date:

Project end date:

Status date:

Percent complete:

Primary forecast method:

Planned spend at status date:

Uncommitted remaining estimate:

Reserve cushion:

Protect this share of the approved budget when interpreting forecast headroom; 0% leaves the base signal unchanged.

Measure	Value	Review meaning	Copy
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A project may have cash left in its budget and still be heading toward an overrun. Posted invoices describe the past. Open purchase orders, booked contractors, unfinished work, schedule position, and the reliability of reported progress determine how much of the apparent headroom is truly available.

Budget burn is a status-date review. Every amount and progress measure should use the same cut-off date. If actual spend runs through Friday but percent complete reflects a report from the previous month, the resulting forecast mixes two different project snapshots and can look more precise than it is.

Approved budget: The amount used as the completion target, similar to budget at completion in earned value management.
Actual spend: Cost posted or invoiced through the status date.
Committed cost: Approved obligations not yet included in actual spend, such as purchase orders and booked contract work.
Percent complete: The share of planned work actually accomplished, preferably supported by accepted deliverables or weighted milestones.

No single forecasting method fits every cost profile. A time-based forecast assumes spend grows in proportion to elapsed schedule time. A percent-complete forecast assumes actual cost grows in proportion to accomplished work. A planned-spend ratio compares actual cost with the baseline value planned by the status date. A manual remaining estimate relies on a current bottom-up view of unfinished work.

Comparing methods exposes assumptions that a single number can hide. Front-loaded procurement can make time-based burn look alarming even when delivery is on plan. Informal progress estimates can make a percent-complete forecast optimistic. A stale planned-spend baseline can distort a planned-ratio forecast, while a manual estimate can omit work that has not yet been scoped.

Earned value measures add cost and schedule context. Cost performance index (CPI) compares the budgeted value of completed work with actual cost. Schedule performance index (SPI) compares completed work with planned value. To-complete performance index (TCPI) estimates the cost efficiency needed on remaining work to finish within the approved budget.

These indicators are review signals, not an audited forecast. Reconcile the accounting ledger, commitments, baseline dates, planned value, scope changes, and progress evidence before moving funding, reducing scope, or reporting an official estimate at completion.

How to Use This Tool:

Build one consistent project snapshot. The chosen currency labels every amount but does not convert between currencies.

Enter the approved Total budget, posted Actual spend to date, and Committed cost in one currency.
Set the approved start and end dates plus the common Status date for cost, commitments, progress, and planned value.
Enter Percent complete from accepted work or weighted milestones rather than a general impression.
Choose the primary forecast method. Planned-spend ratio needs planned spend at the status date; manual remaining needs expected future spend beyond actuals and current commitments.
Add a reserve cushion only when forecast headroom inside that share of the budget should trigger review.
Compare the selected completion forecast with the other available methods, then reconcile any large difference to timing, progress, baseline, or remaining-work assumptions.

Interpreting Results:

Budget after commitments is approved budget minus actual spend and committed cost. A negative value means known spend and obligations already exceed the budget. Forecast variance is budget minus the selected completion forecast; a negative variance signals a modeled overrun.

Runway versus schedule compares the number of days that remaining uncommitted budget would last at the observed actual-spend rate with baseline days remaining. It is meaningful only when elapsed time and actual spend are positive, and it assumes the historical daily burn continues.

CPI below 1 means the budgeted value earned is lower than actual cost.
SPI below 1 means earned value is lower than planned value at the status date.
A higher TCPI means the remaining work must be delivered with greater cost efficiency to stay within budget.
A favorable index or positive variance still needs investigation when progress, planned value, or commitments are incomplete.

Technical Details:

Calendar calculations use whole civil-day intervals between ISO dates. Elapsed schedule time is clamped from the start to the finish for schedule ratios, but actual burn rate uses raw positive days from the start to the status date. A status date outside the baseline therefore produces a review warning instead of silently changing the entered dates.

Formula Core

Known cost exposure is actual spend plus committed cost. Every completion forecast is raised to at least that commitment floor so a method cannot forecast less than cost already spent or obligated.

{Cost}_{floor} = AC + Commitments

Project completion forecast formulas
Method	Raw completion forecast	Required denominator
Time-based burn	Actual spend ÷ elapsed schedule ratio	Elapsed ratio > 0
Percent-complete	Actual spend ÷ completion ratio	Completion ratio > 0
Planned-spend ratio	(Actual spend ÷ planned spend at status) × approved budget	Planned spend > 0
Manual remaining	Actual spend + commitments + uncommitted remaining estimate	Always available with valid nonnegative inputs

The selected final forecast is the larger of its raw forecast and the commitment floor. Forecast variance subtracts that final amount from the approved budget.

EAC = \max ({EAC}_{raw}, {Cost}_{floor})

Earned value is approved budget multiplied by completion ratio. Planned value uses the entered planned spend when it is positive; otherwise it falls back to approved budget multiplied by elapsed schedule ratio.

CPI = \frac{EV}{AC} SPI = \frac{EV}{PV}

TCPI = \frac{BAC - EV}{BAC - AC}

When an index denominator is not positive, its displayed numeric value is zero rather than infinity. Reserve amount is approved budget multiplied by the selected reserve percentage. Total budget must be greater than zero; monetary entries must be nonnegative and no more than one trillion. Percent complete accepts 0% through 100%, reserve accepts 0% through 30%, and dates must be valid calendar dates from 2000 through 2200. Intermediate calculations keep full numeric precision; currency presentation rounds to two decimal places, except JPY presentation uses whole units.

Rule Core

Only one review signal is selected, using this priority order:

Project budget review signal priority
Priority	Signal	Condition
1	Method needs input	The selected forecast denominator is not positive.
2	Commitments exceed budget	Actual spend plus commitments is greater than the approved budget.
3	Forecast overrun	Forecast variance is below zero.
4	Runway shortfall	Positive burn exists and budget runway is shorter than baseline time remaining.
5	Reserve watch	A reserve is set and forecast variance is less than or equal to the reserve amount.
6	Budget on track	None of the higher-priority conditions applies.

Limitations and Privacy:

The calculation runs in the browser and does not send the entered budget snapshot to a calculation service. It is still an educational planning estimate rather than an accounting record, approved baseline, or financial recommendation.

Forecast methods assume simple proportional relationships and do not model irregular procurement, milestone payments, inflation, foreign exchange, scope changes, or probabilistic risk.
Percent complete and planned value must be supported by the same work breakdown and status date as actual cost.
Committed cost must exclude amounts already included in actual spend to avoid double counting.
The reserve cushion creates a review warning only; it does not add reserve to the budget or forecast.

Worked Examples:

Halfway through the baseline

A project has a $100,000 budget, $40,000 actual spend, $8,000 committed cost, 45% completion, and a 100-day baseline with 50 days elapsed. Time-based burn forecasts $80,000 at completion. Percent-complete forecasts about $88,888.89, planned-spend ratio also forecasts $80,000 when planned spend is $50,000, and a $42,000 manual remaining estimate forecasts $90,000.

The selected time-based result leaves $20,000 forecast variance. Current burn is $800 per day and the $52,000 budget remaining after commitments provides 65 days of runway, 15 days more than the baseline time remaining. CPI is 1.125, SPI is 0.90, and TCPI to budget is about 0.917. The differing forecasts are a reason to review progress and remaining work, not to average the four numbers automatically.

References:

Earned Value Management Tutorial, National Aeronautics and Space Administration, updated June 2026.
Earned Value Management Reference Guide for Project-Control Account Managers, National Aeronautics and Space Administration, August 2015.