Enter the used PTO hours and the total PTO hours into the calculator to determine the PTO percentage.
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PTO Percentage Formula
The calculator uses three formulas, one for each tab.
Paid time off used:
PTO% = (PTO used / Total PTO allowance) * 100
PTO balance by date:
Balance = Starting balance + (Annual allowance * Periods elapsed / Periods per year) - PTO used
Power take-off speed percentage:
PTO% = (Driven RPM / Engine RPM) * 100
For hydraulic mode, the driven RPM is calculated first:
Pump RPM = (GPM * 231) / Displacement / Efficiency
Variables:
- PTO used: hours or days of paid time off already taken
- Total PTO allowance: total hours or days available for the period
- Starting balance: hours carried into the accrual period
- Annual allowance: full-year PTO grant
- Periods elapsed: completed accrual periods between the start and balance dates
- Engine RPM: engine speed while the PTO is engaged
- Driven RPM: required speed at the driven shaft or pump
- GPM: target hydraulic flow in gallons per minute
- Displacement: pump volume per revolution in cubic inches
- Efficiency: pump volumetric efficiency as a decimal
The first tab divides used PTO by the total allowance to give the percentage consumed. The second tab adds accrued hours to a starting balance and subtracts hours used to project a balance on a chosen date. The third tab compares driven shaft speed to engine speed to give the PTO speed ratio as a percentage. In hydraulic mode it back-solves the pump RPM from the target flow before doing the ratio.
Reference Tables
Common annual PTO allowances in the United States, expressed in hours assuming an 8-hour day:
| Tenure | Days/year | Hours/year | Accrual per biweekly period |
|---|---|---|---|
| Under 1 year | 10 | 80 | 3.08 hr |
| 1 to 5 years | 15 | 120 | 4.62 hr |
| 5 to 10 years | 20 | 160 | 6.15 hr |
| 10+ years | 25 | 200 | 7.69 hr |
Typical mechanical PTO speed ratios for truck-mounted equipment:
| Application | Typical PTO % | Example at 1500 engine RPM |
|---|---|---|
| Dump truck hoist | 70 to 80% | 1050 to 1200 RPM |
| Refuse packer | 85 to 100% | 1275 to 1500 RPM |
| Aerial lift | 100 to 125% | 1500 to 1875 RPM |
| Vacuum truck blower | 125 to 150% | 1875 to 2250 RPM |
Examples and FAQ
Example 1: Paid time off used. You have a 120-hour annual PTO allowance and have taken 6 days at 8 hours per day. Used hours = 48. Percentage = 48 / 120 × 100 = 40%. You have 72 hours, or 9 days, remaining.
Example 2: PTO speed ratio. A hydraulic pump needs 12 GPM. The pump displaces 2.0 cubic inches per revolution at 90% efficiency. Pump RPM = 12 × 231 / 2.0 / 0.90 = 1540 RPM. With the engine at 1400 RPM, the PTO percentage = 1540 / 1400 × 100 = 110%.
Does the calculator account for holidays in accrual? No. The accrual tab counts calendar days or completed pay periods between the two dates. Subtract holiday hours from the PTO used field if your policy treats them separately.
What hours per day should you use? Use the value your employer applies when converting a PTO day to hours. Most full-time policies use 8. Part-time schedules may use 4, 6, or another number.
Why is my PTO speed ratio above 100%? The driven equipment runs faster than the engine. This is normal for pumps and blowers that need high shaft speed. Confirm your PTO model supports the ratio and torque at that speed.
What if used PTO exceeds the allowance? The result will show over 100%. This usually means you have borrowed against future accrual or taken unpaid leave. Check with payroll on how the overage is handled.