Drilling Calculator
Calculate RPM, feed rate, thrust force, torque, and machining time for drilling operations
This free online drilling calculator provides instant results with no signup required. All calculations run directly in your browser — your data is never sent to a server. Supports both metric (SI) and imperial units with built-in unit selection dropdowns on every input field, so you can work in whatever units your problem provides. Designed for engineering students and professionals working through coursework, design projects, or quick reference calculations.
Drilling Calculator
Results
Thrust = Kf·f^0.8·D | Torque = Kf·f^0.8·D²/4 | Time = depth/(f·N)
Thrust and torque are empirical estimates. Kf varies with workpiece material, drill geometry, and coating.
Thrust, Torque and Power vs Feed Rate
Thrust on the left axis (N); torque (N·m) and power (kW) on the right axis. Marker shows the current feed.
Tip: hover to read values, click to pin a point for export
How to Use This Calculator
Enter your input values
Fill in all required input fields for the Drilling Calculator. Most fields include unit selectors so you can work in your preferred unit system — metric or imperial, whichever matches your problem.
Review your inputs
Double-check that all values are correct and that you have selected the right units for each field. Incorrect units are the most common source of calculation errors and can produce results that are off by factors of 2, 10, or more.
Read the results
The Drilling Calculator instantly computes the output and displays results with units clearly labeled. All calculations happen in your browser — no loading time and no data sent to a server.
Explore parameter sensitivity
Try adjusting individual input values to see how the output changes. This is a quick and effective way to develop intuition about how different parameters influence the result and to identify which inputs have the largest effect.
Formula Reference
Spindle Speed from Cutting Speed
N = 1000·v/(π·D)
Variables: N = spindle speed (rev/min), v = cutting speed at the drill periphery (m/min), D = drill diameter (mm; entered in mm or in, stored internally in m and multiplied by 1000), 1000 = metre-to-millimetre conversion (mm/m), π = 3.14159 (dimensionless). Source: Groover, Fundamentals of Modern Manufacturing, 7th ed., Ch. 22 (Drilling and Related Hole-Making Operations); Machinery's Handbook, 31st ed., Speeds and Feeds section
Feed Rate and Machining Time
vf = f·N | tm = ℓ/vf = ℓ/(f·N)
Variables: vf = feed rate / penetration rate (mm/min), f = feed per revolution (mm/rev), N = spindle speed (rev/min), ℓ = hole depth (mm; entered in mm, stored in m and multiplied by 1000), tm = machining time (min). Note: this tool uses tm = ℓ/vf only. Groover's full expression is tm = (ℓ + A)/vf, where A = drill-point approach allowance (mm; about 0.3·D for a standard 118° point); the allowance, plus breakthrough, dwell, peck-retract and rapid-approach time, is not included, so actual cycle time is longer. Source: Groover, Fundamentals of Modern Manufacturing, 7th ed., Ch. 22 (Machining Time in Drilling)
Drilling Thrust Force (specific-force model)
Ft = Kf·f^0.8·D
Variables: Ft = axial thrust force (N), Kf = lumped empirical material coefficient (N/mm^1.8; presets 350 aluminium alloys, 700 gray cast iron, 1400 carbon steel, 1800 alloy steel, 2000 stainless steel, or user-entered), f = feed per revolution (mm/rev), D = drill diameter (mm). The 0.8 exponent is the Kienzle form f^(1−mc) with mc ≈ 0.2; the D^1.0 exponent follows from two cutting lips of radial engagement D/2 each at chip thickness f/2. Caveat: the chisel-edge thrust component (which scales as D², independent of feed) is folded into Kf rather than modelled separately, so thrust is under-predicted at feeds below roughly 0.1 mm/rev. Source: Kienzle specific-cutting-force model, kc = kc1.1·h^(−mc) — König & Klocke, Fertigungsverfahren Bd. 1 (Drehen, Fräsen, Bohren), drilling force chapter; Sandvik Coromant Technical Guide, drilling formulas and definitions. This is deliberately not the Shaw–Oxford correlation of Shaw, Metal Cutting Principles, 2nd ed. and Machinery's Handbook, which instead gives thrust ∝ f^0.8·D^0.8 plus a separate chisel-edge term.
Drilling Torque and Cutting Power
M = Kf·f^0.8·D²/4 = Ft·D/4 | P = 2·π·N·M/(60·10⁶) = Kf·f^0.8·D·v/(120·10³)
Variables: M = drilling torque (N·mm; also reported as M/1000 in N·m), Ft = axial thrust force (N), Kf = lumped empirical material coefficient (N/mm^1.8), f = feed per revolution (mm/rev), D = drill diameter (mm), N = spindle speed (rev/min), v = cutting speed at the periphery (m/min), P = cutting power at the tool (kW), 60 = min-to-s conversion (s/min), 10⁶ = N·mm/s-to-kW conversion ((N·mm/s)/kW), 120·10³ = combined conversion for D in mm and v in m/min ((N·m/min)/kW). The D²/4 form places the resultant cutting force at a mean radius of D/4, so M ≡ Ft·D/4 identically — one coefficient Kf therefore fixes both torque and thrust, and cannot be calibrated to measured torque and measured thrust independently as Kienzle's separate kc and kf allow. P is power at the cutting edge, not spindle motor power: divide by drive efficiency (typically 0.7–0.9) for motor sizing. Source: König & Klocke, Fertigungsverfahren Bd. 1, drilling torque and power; Sandvik Coromant Technical Guide, drilling power Pc = f·vc·D·kc/(240·10³); Groover, Fundamentals of Modern Manufacturing, 7th ed., Ch. 21 (Power and Energy Relationships in Machining)
When to Use This Calculator
- •Use the Drilling Calculator when solving homework or exam problems that require quick numerical verification of your hand calculations — instant feedback helps identify arithmetic errors before they propagate.
- •Use it during the early design phase to rapidly iterate on parameters and narrow down feasible configurations before committing time to detailed finite element simulations or full design packages.
- •Use it when reviewing a colleague's calculation or checking a vendor's data sheet for plausibility — a quick sanity check can prevent costly downstream errors.
- •Use it to generate reference data for a technical report or presentation without manual computation, ensuring consistent, reproducible numbers throughout the document.
- •Use it in the field when a quick estimate is needed and a full engineering software package is not available.
About This Calculator
The Drilling Calculator is a precision engineering calculation tool designed for students, engineers, and technical professionals. Calculate RPM, feed rate, thrust force, torque, and machining time for drilling operations All calculations are performed using established engineering formulas from the relevant scientific literature and standards. Inputs support both metric (SI) and imperial unit systems, with unit conversion handled automatically — simply select your preferred unit from the dropdown next to each field. Results are computed instantly in the browser without sending data to a server, ensuring both speed and privacy. This calculator is intended as a supplementary tool for learning and design exploration; always verify results against authoritative references for safety-critical applications.
The Theory Behind It
Drilling is the process of creating round holes using a rotating multi-edge cutting tool (drill). The drilling parameters include: drill diameter D, rotational speed N (RPM), feed rate f (mm/rev or IPR), cutting speed V_c = π·D·N/1000 (m/min), and penetration rate V_f = f·N (mm/min). Drilling has unique characteristics compared to other machining: (1) the chisel edge at the drill center has zero cutting speed and effectively extrudes rather than cuts, creating thrust force; (2) chip evacuation is critical — chips must exit through the drill flutes against the incoming material; (3) deep holes (more than 3-5 diameters) require peck drilling or coolant-through drills to evacuate chips and reduce friction. Cutting parameters for drilling steel: HSS drill 20-30 m/min, carbide 60-150 m/min, TiN-coated HSS 30-40 m/min. Feed rate scales with drill diameter — typical f = 0.01×D to 0.02×D mm/rev (e.g., 0.1-0.2 mm/rev for a 10 mm drill). Thrust force F_t ≈ K·f × D, where K is a material constant (40-70 N/mm² for steel). Torque τ ≈ K'·f·D², where K' is another material constant. Machining time t = depth/(f·N). The calculator computes drilling parameters, thrust force, torque, and machining time for given material and drill size.
Real-World Applications
- •Production drilling: compute feed, speed, and time for mass-produced holes in manufacturing. Critical for job costing and scheduling.
- •Drill press and machine capacity: verify that the machine has sufficient thrust capability and torque for the drill size and material.
- •Shop-floor drill speed charts: machinists use RPM tables indexed by drill diameter and material type, derived from cutting speed formulas.
- •Deep hole drilling: special drills (gun drills, BTA) drill holes with aspect ratios > 20:1 at specialized parameters different from ordinary twist drills.
- •Multi-spindle drilling: gang drills and multi-spindle heads for high-volume production use simultaneous drilling with optimized individual drill parameters.
Frequently Asked Questions
What RPM should I use for drilling?
N = V_c × 1000 / (π × D), where V_c is cutting speed (m/min) and D is drill diameter (mm). For a 10 mm HSS drill at V_c = 25 m/min: N = 25 × 1000 / (π × 10) = 796 RPM. Smaller drills need higher RPM to maintain cutting speed; larger drills need lower RPM. Published drill speed charts use diameter and material to give recommended RPM directly.
What's the feed rate for drilling?
Typical f = 0.01×D to 0.02×D mm/rev, where D is drill diameter in mm. A 6 mm drill: 0.06-0.12 mm/rev. A 12 mm drill: 0.12-0.24 mm/rev. Steel uses the lower end of this range, aluminum the upper. Thin sheet material uses reduced feeds. Deep holes use reduced feeds with peck drilling to evacuate chips.
How do I compute drilling machining time?
t = L / (f × N), where L is hole depth plus drill tip allowance (approx 0.3×D for 118° drill point), f is feed in mm/rev, and N is RPM. For a 20 mm deep hole with 6 mm drill at f = 0.1 mm/rev and 1500 RPM: t = (20 + 1.8) / (0.1 × 1500) = 21.8 / 150 = 0.145 min = 8.7 seconds.
Why is drilling thrust force important?
Thrust force is the axial force needed to push the drill into the workpiece. It depends on feed rate, drill diameter, and material: F_t ≈ K × f × D, with K around 50-70 N/mm² for steel. For a 10 mm drill in steel at f = 0.15 mm/rev: F_t ≈ 60 × 0.15 × 10 = 90 N... but actual force is higher including chisel edge component (total 2-3× this). The drill press or CNC spindle must provide this force; insufficient machine thrust limits drilling capability.
What's peck drilling?
Peck drilling involves periodically retracting the drill to break chips and allow coolant to reach the drill tip. Used for deep holes (aspect ratio > 3:1) where chip evacuation is otherwise impossible. Each peck cycle consists of drilling a small increment, retracting fully or partially, and re-entering. Modern CNCs have peck cycles built in as canned cycles. Coolant-through drills enable deep-hole drilling without pecking by flushing chips out through internal channels.
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References & Further Reading
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