Billable Hours Calculator

Entry mode:

Timer captures use duration rows; clock rows support same-day or explicitly enabled overnight work.

Billing increment:

Six minutes is one tenth of an hour; use the increment required by the engagement or billing policy.

Rounding direction:

Select the direction stated by the client guideline or agreement.

Write-down basis:

The selected basis applies to the write-down value in every row.

Overnight clock rows:

Leave off to flag reversed times; enable only when clock rows genuinely cross midnight.

Time entries:

Use one row per invoice task. Keep client or matter details anonymous before sharing the URL.

Date	Client / project	Description	Duration	Unit	Start	End	Hourly rate	Billable	{{ writeDownHeading }}	Remove
{{ `Entry ${index + 1} date` }}	{{ `Entry ${index + 1} client or project` }}	{{ `Entry ${index + 1} description` }}	{{ `Entry ${index + 1} duration` }}	{{ `Entry ${index + 1} duration unit` }}	{{ `Entry ${index + 1} start time` }}	{{ `Entry ${index + 1} end time` }}	{{ `Entry ${index + 1} hourly rate` }} {{ safeCurrencySymbol }}	{{ `Entry ${index + 1} billable status` }}	{{ `Entry ${index + 1} write-down` }}

Group totals by:

Use project for invoice review, date for daily review, or status for billable versus internal time.

Currency symbol:

Use a symbol or short code such as $, RM, EUR, or GBP.

Export label:

Add a short client, matter, or billing-period reference.

Entry	Recorded	Rounded	Rate	Gross	Write-down	Net	Copy
{{ row.project }}{{ row.date }} · {{ row.description }}	{{ formatHours(row.rawHours) }}	{{ formatHours(row.roundedHours) }}	{{ formatMoney(row.rate) }}/hr	{{ formatMoney(row.grossAmount) }}	{{ formatMoney(row.writeDownAmount) }}	{{ row.billable ? formatMoney(row.netAmount) : 'Non-billable' }}

Group	Entries	Billable	Non-billable	Gross	Write-down	Net	Copy
{{ row.label }}	{{ row.entries }}	{{ formatHours(row.billableHours) }}	{{ formatHours(row.nonBillableHours) }}	{{ formatMoney(row.grossAmount) }}	{{ formatMoney(row.writeDownAmount) }}	{{ formatMoney(row.netAmount) }}

Entry	Billing status	Adjustment	Gross	Net	Review note	Copy
{{ row.project }}	{{ row.billable ? 'Billable' : 'Non-billable' }}	{{ row.adjustment }}	{{ formatMoney(row.grossAmount) }}	{{ formatMoney(row.netAmount) }}	{{ row.note }}

Billable time becomes an invoice only after several policy choices have been applied. Recorded minutes may be rounded to an agreed increment, non-billable work must be excluded, an hourly rate turns time into a gross charge, and a write-down may reduce that charge before the client sees it. Two people can record the same work and produce different totals if they use different increments or round in different directions.

A useful billing record keeps the original duration beside the rounded duration. That difference shows how much time the billing rule added or removed and makes short entries easier to audit. Six-minute increments are common because six minutes equals one tenth of an hour, but the correct increment and direction come from the engagement, employer policy, contract, professional duties, and applicable law.

Recorded time describes the work as captured by a duration, timer, or start and end times.
Rounded time is the billable duration after the selected increment and direction are applied to each row.
Gross amount is rounded billable time multiplied by the row's hourly rate.
Net amount is gross amount minus any bounded write-down.
Realization compares net amount with gross amount; it does not measure utilization, collection, profitability, or work quality.

Row-level rounding matters because rounding a day's total once is not the same as rounding each task separately. Ten seven-minute tasks rounded upward to six-minute increments become 120 billed minutes, while the 70-minute combined duration rounded once becomes 72 minutes. The tool follows row-level billing, so each task should occupy the row that the governing policy expects.

Write-downs also need a stated basis. Ten percent, ten currency units, and ten hours are fundamentally different adjustments. A sound review keeps the selected basis visible and checks capped adjustments, zero rates on billable rows, and rates attached to non-billable rows before totals are used.

The arithmetic can support invoice preparation, but it cannot decide whether a fee or rounding practice is permitted, reasonable, or contractually agreed. Keep contemporaneous records, use descriptive entries, and review the result against the actual engagement and jurisdiction before billing.

How to Use This Tool:

Choose the billing policy first so every row is processed consistently.

Select Duration rows for entered hours or minutes, or Start and end time rows for clock times. Enable overnight rows only when an end time genuinely falls on the next day.
Choose the Billing increment and Rounding direction stated by the applicable policy or agreement.
Choose whether write-down values represent a percentage, flat amount, or rounded hours removed.
Use one row per invoice task. Enter its date, client or project, description, time, rate, billable status, and any write-down.
Read the Adjustment review before relying on totals. Correct reversed times and warning rows, compare recorded with rounded time, then use grouped totals and realization only after the rows match the source record.

Interpreting Results:

Net billable value is the sum of billable row amounts after rounding and write-downs. Non-billable rows contribute rounded hours to the non-billable total but contribute no gross or net charge.

Billable hours result checks
Result	Read it as	Check before use
Rounded delta	Rounded minutes minus recorded minutes	Large positive or negative changes may indicate the wrong increment or row granularity.
Realization	Net ÷ gross × 100%	A low percentage can reflect write-downs, not poor timekeeping; 100% says nothing about collection.
Effective rate	Net amount ÷ rounded billable hours	It is based on billed hours after rounding, not all recorded or non-billable work.
Group totals	The same rows grouped by project, date, or billable status	Changing the grouping does not change line values or overall totals.

The displayed currency symbol is a label only. It does not convert rates or amounts, so every monetary row must already use the same currency.

Technical Details:

Each row is normalized to non-negative minutes. Duration rows convert hours by multiplying by 60. Clock rows subtract start minutes from end minutes; when overnight handling is enabled, a negative difference receives 1,440 minutes so the end is treated as the following day.

Formula Core

Rounding works in units of the selected increment. Up uses the next unit, down uses the previous unit, and nearest uses the closest unit for non-negative time.

m_{rounded} = I \times f_{direction} (\frac{m_{raw}}{I})

A billable row converts rounded minutes to hours, multiplies by rate, rounds the gross to cents, applies one bounded write-down, and rounds the resulting money values to cents.

G = cents (\frac{m_{rounded}}{60} \times r), N = \max (0, cents (G - D))

The write-down depends on the selected basis and can never exceed the row's gross amount.

Billable hours write-down formulas
Basis	Write-down amount D	Cap
Percent	gross × min(entered percent, 100) ÷ 100	100% of gross
Flat amount	min(entered amount, gross)	gross amount
Hours removed	min(entered hours, rounded hours) × rate	all rounded hours

Totals add the already processed rows. Realization and effective rate are derived from those totals.

Realization = \frac{N_{total}}{G_{total}} \times 100 %, r_{effective} = \frac{N_{total}}{h_{billable}}

If gross amount or billable hours is zero, the corresponding ratio is reported as zero rather than divided by zero. Time keeps full minute precision after input conversion; money rounds at row gross, row write-down, row net, and aggregate monetary totals.

A worksheet accepts 1–12 rows. Duration values run from 0 to 10,000 in their selected unit, hourly rates from 0 to 1,000,000, and write-downs must be non-negative. Clock values must be valid 24-hour times; an end before its start is rejected unless overnight handling is enabled.

Accuracy and Privacy Notes:

Billing rules are contractual and jurisdiction-dependent. This worksheet applies the selected arithmetic consistently but does not determine whether the chosen increment, direction, rate, description, or adjustment is lawful or professionally appropriate.

Review every warning and compare the rows with the original contemporaneous record.
Calculations run in the browser, but the current page address can carry entered state for sharing. Remove client, matter, and confidential work details before copying that address or exporting a record.
Do not combine currencies. The symbol changes presentation only.
Realization excludes collection, expenses, taxes, profitability, and non-billable effort.

Worked Examples:

Seven-minute call with an upward six-minute rule

A 7-minute billable call rounds up to 12 minutes, or 0.2 hours. At 100 per hour, gross is 20. A 10% write-down removes 2, leaving net value of 18, 90% realization, and an effective rate of 90 per rounded billable hour. The 5-minute rounding delta is the figure to verify against the engagement's policy.

References:

29 CFR 785.48: Use of Time Clocks, Electronic Code of Federal Regulations.
FAR 52.232-7: Payments under Time-and-Materials and Labor-Hour Contracts, U.S. General Services Administration.
Model Rule 1.5: Fees, American Bar Association.